Glossary of Natural Resources and Environmental Pollution Control

Abstract

This chapter presents the technical terms and acronym terms in the wide academic areas of environmental engineering and natural resources management. The authors have tried their best to selectively cover the subject areas in the Handbook of Environmental Engineering (HEE), Volume 19 (Environmental and Natural Resources Engineering), Volume 20 (Integrated Natural Resources Management), Volume 21 (Environmental Flotation Engineering), and Volume 22 (Integrated Natural Resources Research).

Glossary of Natural Resources and Environmental Pollution Control [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]

100-Year flood levels

Severe flood levels with a one-in-100 likelihood of occurring in any given year.

Abrupt climate change

Sudden (on the order of decades), large changes in some major component of the climate system, with rapid, widespread effects.

Absconding swarm

It is an entire colony of bees, which abandons the hive, often because of disease, wax moth, excessive heat or water, lack of resources, or other reasons.

Absconding swarm

It is an action when an entire colony of bees abandons the hive, often because of disease, wax moth, excessive heat or water, lack of resources, or other reasons

Acidity

It is the capacity of water or wastewater to neutralize bases. Acidity is expressed in milligrams per liter of equivalent calcium carbonate.

Acinetobacter

A common heterotrophic bacteria that functions as a phosphorus-accumulating organism (PAO) in biological phosphorus removal process.

Activated carbon adsorption, granular

Granular activated carbon (GAC) is used in both water and wastewater treatment. GAC systems generally consist of vessels in which the carbon is placed, forming a “filter” bed. These systems can also include carbon storage vessels and thermal regeneration facilities. Vessels are usually circular for pressure systems or rectangular for gravity flow systems. Once the carbon adsorptive capacity has been fully utilized, it must be disposed of or regenerated. Usually multiple carbon vessels are used to allow continuous operation. Columns can be operated in series or parallel modes. All vessels must be equipped with carbon removal and loading mechanisms to allow for the removal of spent carbon and the addition of new material. Flow can be either upward or downward through the carbon bed. Vessels are backwashed periodically. Surface wash and air scour systems can also be used as part of the backwash cycle. Small systems usually dispose of spent carbon or regenerate it offsite. Systems above about 3 to 5 MGD (million gallons per day) usually provide on-site regeneration of carbon for economic reasons.

Activated carbon adsorption, powdered

Powdered activated carbon (PAC) is used in both water and wastewater treatment. For water treatment, PAC systems generally involve dosing powdered activated carbons in slurry form to rapid mixers and flocculators (for mixing and flocculation, and adsorption) before reaching clarifiers for PAC-floc separation and clarifier effluent discharge. For wastewater treatment, powdered activated carbon in slurry form is dosed to either mixing/flocculation chambers (if they exist), or to an aeration basin directly to be mixed with mixed liquor for adsorption reactions. The spent PAC again is recovered or removed by a subsequent clarifier (either sedimentation clarifier or flotation clarifier). When PAC is used in conjunction with a flotation clarifier, it is also called “adsorption flotation.”

Activated carbon

It is a porous carbon adsorbent with many micropores, microchannels, and high surface area for adsorption (removal) of mainly soluble organic substances, color, odor, and some inorganic heavy metals from water or air. There are three kinds of activated carbons: (a) powdered activated carbon; (b) granular activated carbon; and (c) cloth or fiber-type activated carbon.

Activated sludge

They are sludge particles produced in raw or settled wastewater (primarily effluent) by the growth of organisms (including zoogleal bacteria) in aeration tanks in the presence of dissolved oxygen. The term “activated” comes from the fact that the particles are teeming with bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living organisms, which can feed on the incoming wastewater.

Activated sludge process

(a) It is a continuous flow, biological treatment process characterized by a suspension of aerobic microorganisms, maintained in a relatively homogeneous state by the mixing and turbulence induced by aeration. The microorganisms are used to oxidize soluble and colloidal organics to carbon dioxide and water in the presence of molecular oxygen. The process is generally, but not always, preceded by primary clarification (either primary sedimentation clarification or primary flotation clarification). The mixture of microorganisms and wastewater formed in the aeration basins, called mixed liquor (ML), is transferred to secondary clarification (either secondary sedimentation clarification or secondary flotation clarification) for liquid-solid separation. The major portion of the microorganisms separated from the secondary clarifiers (secondary sedimentation clarifiers or secondary flotation clarifiers) is recycled to the aeration basins to be mixed with incoming wastewater, while the excess, which constitutes the waste activated sludge (WAS), is sent to the sludge-handling facilities. The rate and concentration of the returned activated sludge (RAS) returned to the aeration basins determines the mixed liquor suspended solids (MLSSs) level developed and maintained in the aeration basins. During the oxidation process , a certain amount of the organic material is synthesized into new cells, some of which then undergoes auto-oxidation (self-oxidation, or endogenous respiration) in the aeration basins, the remainder forming net growth or excess sludge. Oxygen is required in the process to support the oxidation and synthesis reactions. In the conventional activated sludge plant, the wastewater is commonly aerated for a period of 4 to 8 hours (based on average daily flow) in a plug flow hydraulic mode. Either surface or submerged aeration systems can be employed to transfer oxygen from air to wastewater. (b) It is a suspended-growth biological wastewater treatment process, which speeds up the decomposition of wastes in the wastewater being treated. Activated sludge is added to wastewater, and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or refused (returned to the aeration tank) as needed. The remaining wastewater then undergoes more treatment.

Adaptation

Adjustment or preparation of natural or human systems to a new or changing environment, which moderates harm or exploits beneficial opportunities.

Adaptive capacity

The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.

Adsorption flotation

When powdered activated carbon (PAC) is used in conjunction with a flotation clarifier for water or wastewater treatment, the unit process is also called “adsorption flotation.”

Advanced waste treatment

It is any process of water renovation that upgrades treated wastewater beyond secondary treatment to meet specific reuse requirements. Typical processes include chemical treatment, granular activated carbon, and pressure filtration. Also called tertiary treatment.

Advisory

A notice that highlights special weather conditions that are less serious than a warning. They are for events that may cause significant inconvenience, and if caution is not exercised, the conditions could lead to situations that may threaten life and/or property.

Aeration

The process of adding air to water. In wastewater treatment, air is added to refresh wastewater and to keep solids in suspension. With mixtures of wastewater and activated sludge, adding air provides mixing and oxygen for the microorganisms treating the wastewater.

Aerobes

Bacteria that must have molecular (dissolved) oxygen (DO) to survive.

Aerobic bacteria

These bacteria live, remove BOD, and reproduce themselves under aerobic environmental conditions containing sufficient dissolved oxygen (DO).

Aerobic digestion

The process equipment of aerobic digestion is similar to that of the activated sludge process. Aerobic digestion is not a suspended-growth biological process in principle, and is for sludge treatment (not for wastewater treatment). It is a suspended-destruction biological process. In the presence of oxygen, the biodegradable matter in the activated sludge (biosolids) is oxidized, destroyed, and converted to carbon dioxide and water. Oxygen must be supplied in direct proportion to the mass of volatile solids (VSs) destroyed. Sludge stabilization is not complete until there has been an extended period of primarily endogenous respiration (15 to 20 days).

Aerobic

An environmental condition in which free and dissolved oxygen is available in an aqueous environment (For instance, nitrification is an aerobic process).

Aerosols

Small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight depending on their composition.

Afforestation

Planting of new forests on lands that historically have not contained forests.

After-action findings

Documented results of what in your emergency plan worked and did not work after an incident happens. These findings are used to improve your plan and procedures.

Air lift

It is a type of pump. This device consists of a vertical riser pipe in the wastewater or sludge to be pumped. Compressed air is injected into a tall piece at the bottom of the pipe. Fine air bubbles mix with the wastewater or sludge to form a mixture lighter than the surrounding water, which causes the mixture to rise in the discharge pipe to the outlet. An air lift pump works like the center of a stand in a percolator coffee pot.

Albedo

The amount of solar radiation reflected from an object or surface, often expressed as a percentage.

Algae

They are microscopic plants, which contain chlorophyll and live floating or are suspended in water. They also may be attached to structures, rocks, or other similar substances. Algae produce oxygen during sunlight hours and use oxygen during night hours. Their biological activities appreciably affect the pH and dissolve oxygen of the water.

Aliquot

It is a portion of a sample, which is often an equally divided portion of a sample.

Alkali bee (Nomia melanderi)

These bees are important pollinators, especially of alfalfa. Reared in large numbers, the bees are released in areas near this crop, resulting in a greatly increased yield of alfalfa. Each female takes about 30 days to build a single nest of about 20 cells. The bees hibernate in the prepupa stage and complete their life cycle the second year.

Alkalinity

The capacity of water to neutralize acids by the water’s content of carbonates, bicarbonates, hydroxide, and other compounds, also known as buffering capacity.

Alternative energy

Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).

Ammonia nitrogen

Elemental nitrogen present in the form of ammonia (NH₃).

Ammonia stripping

It is a physicochemical desorption process for removing ammonia content from a wastewater by a gas-stripping operation. In the process, wastewater at elevated pH is pumped to the top of a packed tower with a countercurrent flow of air drawn through the bottom openings. Free ammonia (NH₃) is stripped from the falling water droplets into the air stream, which is then discharged to the atmosphere. Lime or caustic soda is added prior to the stripping to raise the pH of the wastewater to the range of 10.8 to 11.5, converting essentially all ammonium ions to ammonia gas, which can then be stripped by air. Process controls required for the operation are the proper pH adjustment of the influent wastewater, and maintenance of proper air and water flows. Ammonia removal efficiency is highly dependent on air temperature and air/water ratios. As the air temperature decreases, the efficiency drops significantly. For instance, the ammonia removal efficiency can be 75% at air temperature of 10 ° C, while the ammonia removal efficiency can be 90–95% at air temperature of 20 ° C. Very poor ammonia removal efficiency will be experienced in cold weather location (0 to 10 ° C). The influent wastewater should always be clarified before stripping. Residual ammonia in the ammonia stripping effluent can be removed by breakpoint chlorination. The countercurrent flow ammonia stripping process is technically and economically feasible for a wastewater containing about 10–100 mg/L of ammonia.

Ammonification

A biochemical or chemical process in which soluble organic nitrogen is converted to ammonia.

Anaerobic

(a) An environmental condition in which free, dissolved, and combined oxygen is unavailable in an aqueous environment (i.e., dissolved oxygen = 0 mg/L); (b) A condition in which atmospheric or dissolved molecular oxygen is NOT present in the aquatic (water) environment.

Anaerobic bacteria

They are bacteria that live and reproduce in an environment containing no “free” or dissolved oxygen. Anaerobic bacteria obtain their oxygen supply by breaking down chemical compounds, which contain oxygen, such as sulfate (SO₄ ²⁻).

Anaerobic digestion

This is a biological destruction process for destroying biodegradable organic sludge (biosolids) in the absence of molecular oxygen, or under anaerobic conditions. It is a three-stage sludge stabilization process for sludge volume reduction: (a) hydrolysis stage: breakdown of particulate matter and large macromolecules; (b) acid formation stage: fermentation of the soluble organic matter formed in the first reaction to volatile acids; (c) methanogenesis stage: conversion of the volatile acids to the stable end produces, such as methane gas, carbon dioxide gas, and water. Four anaerobic digestion operational modes are available: (a) standard rate digestion mode, or one stage, unheated, and unmixed; (b) high rate digestion mode: one stage, heated, and mixed; (c) two-stage digestion mode; and (d) anaerobic contact process. Anaerobic digestion can occur in two temperature ranges: mesophilic (80–110 ° F) and thermophilic (113–149 ° F). Mesophilic range operation is more stable, while thermophilic range operation offers improved sludge dewatering. The process reduces volatile solids and thereby reduces the overall mass of the sludge, lowering subsequent land disposal costs. Wastewater solids and water (about 5% solids, 95% water) are placed in a large tank where bacteria decompose the solids in the absence of dissolved oxygen.

Analysis (chemical)

The determination of the qualitative and/or quantitative composition of a substance.

Analytical reagent (AR)

The American Chemical Society’s designation for the highest purity of certain chemical reagents and solvents.

Anchor booms

They are parts fitted on some dredges for handling and placing the swing anchors from the dredge without the need of a support vessel, or mounted at the bow and suspended from a gantry or gallows frame.

Anionic polymer (or anionic polyelectrolyte)

A negatively charged electrolyte used as a coagulant to aid in separating (settling or floating) solids in water or wastewater.

Anionic surfactant

A negatively charged surface active agent, such as ABS and LAS, that lowers the surface tension in water, and usually used as a cleaning agent, or as a collector in a flotation process system.

Annual plant

It is a plant that completes its life cycle from germination to the production of seed within one year and then dies.

Anoxic

(a) An environmental condition in which oxygen is only available in a combined form, such as nitrate (NO₃), nitrite (NO₂), or sulfate (SO₄) in an aqueous environment; (b) oxygen deficient or lacking sufficient oxygen, and dissolved oxygen = 0.0 to 0.1 mg/L.

Anthropogenic

Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.

Apiary

It is a bee year or area when/where colonies, hives, and other equipment assembled in one location for beekeeping operations, also known as a bee yard.

Apiculture

It is a career, or business, or hobby of beekeeping; the keeping of bees, particularly on a commercial scale.

Approach

The difference in temperatures of water temperature exiting the tower versus the dry bulb temperature of the air entering the tower.

AquaDAF

It is a rectangular dissolved air flotation (DAF) clarifier commercially available from SUEZ Water Technologies and Solutions, Richmond, VA 23229, USA.

Assimilation

The biological or microbiological process in which nitrogen is taken in by cells to be used for growth and reproduction.

Atmosphere

The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the atmosphere contains water vapor, whose amount is highly variable but typically 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.

Atmospheric lifetime

Atmospheric lifetime is the average time that a molecule resides in the atmosphere before it is removed by chemical reaction or deposition. This can also be thought of as the time that it takes after the human-caused emission of a gas for the concentrations of that gas in the atmosphere to return to natural levels. Greenhouse gas lifetimes can range from a few years to a few thousand years.

Attached-growth biological processes

In an attached-growth biological process system, the biomass responsible for biochemical reactions is attached on the surface of rocks, sands, woods, disks, screens, etc., where the wastewater passes through, and the organic pollutants and nutrients are removed. They include: trickling filters, denitrification filter using coarse media; denitrification filter using fine media, slow sand filters, rotating biological contactors, etc. The effluent from an attached-growth bioreactor discharges to a water-solid separator (sedimentation clarifier, or flotation clarifier, or membrane filter) for further processing.

Attribute

It is a characteristic of a geographic feature, typically stored in tabular format and linked to the feature in a relational database. The attributes of a well-represented point might include an identification number, address, and type.

Autotrophic organisms

Organisms that use carbon dioxide, sunlight, or other inorganic substances for their cell growth (Nitrifying bacteria are autotrophic).

Auxiliary engine

It is used to suitably power the hydraulic system and other auxiliary functions on certain type of dredges.

Bacteria

They are living organisms, microscopic in size, which usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as the result of their life processes.

Baffle

It is a flat board or plate, deflector, guide, or similar device constructed or placed in flowing water, wastewater, or slurry systems to cause more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water, chemical solutions, slurry).

Bar screens

There are two types of bar screens (or racks). The most commonly used, and oldest technology, consists of hand-cleaned bar racks. These are generally used in smaller wastewater treatment plants (WWTPs). The second type of bar screen is the type that is mechanically cleaned, which is commonly used in larger facilities.

Base layer

It is a primary layer for spatial reference, upon which other layers are built. Examples of a base layer typically used are either the parcels, or street centerlines.

Base, alkalinity

(a) A substance, which takes up or accepts protons; (b) A substance, which dissociates (separates) in aqueous solution to yield hydroxyl ions (OH⁻); (c) A substance containing hydroxyl ions, which reacts with an acid to form a salt or which may react with metals to form precipitates; (d) A substance that may raise pH.

Basic plan

A component of an emergency operations plan that describes expected hazards, outlines roles and responsibilities, and explains how you keep the plan current.

Basin

The bottom of the tower, water is collected here after passing the tower.

Beach restoration

It is the act of replenishing the sand loss that occurs naturally over time from tidal cycles, currents, waves, and inclement weather. Beaches that have been restored by dredging are designed to protect local communities from future storm damage and to preserve recreational beach space. Dredges are often used as a primary tool for rebuilding beaches.

Bee

It is an insect with four wings that is related to the wasps, gathers pollen and nectar from flowers from which it makes beebread and honey for food, and usually lives in large colonies. There many kinds of bees, such as, honey bees, bumble bees, cuckoo bees, carpenter bees, leaf-cutting bees, digger bees, alkali bees, and mason bees.

Belt filter press, combined sludge thickening and dewatering

Conditioned sludge is first placed on a gravity drainage section where it is allowed to thicken. In this section, the bulk of the free water is removed from the sludge by gravity. On some units, this section is equipped with a vacuum assist, which enhances drainage and may help to reduce odors. Following gravity drainage, pressure is applied in a low-pressure section, where sludge is squeezed between opposing porous cloth belts. On some units, the low-pressure section is followed by a high-pressure section where the sludge is subjected to shearing forces that induce the release of additional quantities of water from the sludge. The final dewatered sludge cake is removed from the belts by scrapper blades.

Biochemical oxygen demand (BOD)

A biochemical quantitative measure of the amount of oxygen used in the biochemical oxidation of organic matter in a specified time period (usually 5 days), at a specified temperature (usually 20 ° C), and under specified conditions (in the dark).

Biofuels

Gas or liquid fuel made from plant material (biomass); includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline.

Biogeochemical cycle

Movements through the Earth system of key chemical constituents essential to life, such as carbon, nitrogen, oxygen, and phosphorus.

Biological nutrient removal (BNR)

The removal of nitrogen and/or phosphorus by the use of proliferation and selection of certain microbiological populations.

Biological phosphorus removal (BPR)

The biological process of phosphorus removal in wastewater that relies on the proliferation and selection of a microbiological population capable of storing phosphorus in excess of their normal growth requirements. Also called biological nutrient removal (BNR) or enhanced biological phosphorus removal (EBPR).

Biomass

(a) Materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, crops, grasses, tree litter, roots, and animals and animal waste. (b) It is a mass or clump of organic material consisting of living organisms feeding on the wastes in wastewater, dead organisms, and other debris.

Biosolids

(a) It is general term for any organic solids containing carbon, such as activated sludge, septic tank sludge, manure, etc. (b) It is a primarily organic solid product, produced by wastewater treatment processes or agricultural installations, that can be beneficially recycled. The word biosolids is replacing the word biological sludge, or organic sludge.

Biosphere

The part of the Earth system comprising all ecosystems and living organisms, in the atmosphere, on land (terrestrial biosphere) or in the oceans (marine biosphere), including derived dead organic matter, such as litter, soil organic matter, and oceanic detritus.

Biotower

It is one type of trickling filters. A biotower is an attached growth biological process that is used to remove organic matter found in wastewater.

Black carbon aerosol

Black carbon (BC) is the most strongly light-absorbing component of particulate matter (PM), and is formed by the incomplete combustion of fossil fuels, biofuels, and biomass. It is emitted directly into the atmosphere in the form of fine particles (PM2.5).

Blank sample

A clean sample or a sample of matrix processed so as to measure artifacts in the measurement (sampling and analysis) process.

Blank

It is a sample bottle containing only dilution water or distilled water, but the sample being tested is not added. Tests are frequently run on a sample and a blank, and the differences are compared.

Blow-down

Some of the water collected in the basin is exited from the tower rather than recirculated within the tower. This prevents buildup of solids in the water.

Blowoff

It is turbulence in aeration tanks caused by damaged diffusers.

Boat plant

A complete small water or wastewater treatment plant installed on a boat, which can navigate in a lake or river for necessary water or wastewater treatment.

BOD

Biochemical oxygen demand . The rate at which organisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation. BOD measurements are used as a measure of the organic strength of wastes in water.

Booster pump

It is a supplemental dredge type pump used in a dredging operation to increase the distance the slurry can be pumped. A booster is often required when a deposit area is greater than 3500 ft. (about 1 km) from the dredge.

Borehole

Any exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to predict atmospheric composition in earlier years.

Breeding

It is a business or hobby in the context of managing domesticated animals, to cause an animal to produce offspring in a controlled and organized manner.

Briefing

A type of training that is a short meeting to provide information about a specific topic.

Brood

They are immature bees that have not yet emerged from their cells; brood of different ages can be in the form of eggs, larvae, or pupae.

Buffer

(a) It is a zone of a specified distance around a feature; (b) it is a solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.

Buffer solution

It is either called pH buffer or hydrogen ion buffer, which is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it.

Bulking

They are clouds of billowing sludge that occur throughout secondary clarifiers and sludge thickeners when the sludge does not settle properly. In the activated sludge process, bulking is usually caused by filamentous bacteria or bound water.

Bumble bee (Bombus occidentalis)

They are natural bees in black and yellow color. A bumble bee’s body is densely pilose, and its wings are transparent. They are natural important pollinators. They nest in the ground. Although bumble bees are closely related to honey bees, their life cycle is different, because only the young queen overwinters. In the fall, the female will mate with a male and this young queen will overwinter alone, the male dying shortly after mating. As spring approaches, the queen starts a new colony by herself— finding or building a cavity in the ground, laying eggs, developing larvae, constructing the waxen honey pot as initial foods, and waiting for development of worker bee, drone bees, etc.

Business recovery

The identification of the systems in place to continue business and administrative operations after an incident.

Cadmium

A minor metallic element, one of the naturally occurring components in the Earth’s crust and waters, and present everywhere in our environment.

Calibrate

To determine, by measurement or comparison with a standard, the correct value of each scale reading on a meter or other device, or the correct value for each setting of a control knob. The levels of the calibration standards should bracket the range of planned measurements.

Calibration

The checking, adjusting, or systematic standardizing of the graduations of a quantitative measuring instrument.

Calibration curve

The graphical relationship between the known values for a series of calibration standards and instrument responses.

Calibration standard

A substance or reference material used to calibrate an instrument.

Carbon capture and sequestration (CCS)

Carbon capture and sequestration (CCS) is a set of technologies that can greatly reduce carbon dioxide emissions from new and existing coal- and gas-fired power plants, industrial processes, and other stationary sources of carbon dioxide. It is a three-step process that includes capture of carbon dioxide from power plants or industrial sources; transport of the captured and compressed carbon dioxide (usually in pipelines); and underground injection and geologic sequestration, or permanent storage, of that carbon dioxide in rock formations that contain tiny openings or pores that trap and hold the carbon dioxide.

Carbon cycle

All parts (reservoirs) and fluxes of carbon. The cycle is usually thought of as four main reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). The annual movements of carbon, the carbon exchanges between reservoirs, occur because of various chemical, physical, geological, and biological processes. The ocean contains the largest pool of carbon near the surface of the Earth, but most of that pool is not involved with rapid exchange with the atmosphere.

Carbon dioxide

A naturally occurring gas, and also a by-product of burning fossil fuels and biomass, as well as land-use changes and other industrial processes. It is the principal human-caused greenhouse gas that affects the Earth’s radiation balance. It is the reference gas against which other greenhouse gases are measured and therefore has a global warming potential of 1.

Carbon dioxide equivalent (CDE)

A metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCO₂Eq).” The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by the associated GWP. MMTCO₂Eq = (million metric tons of a gas) * (GWP of the gas)

Carbon dioxide fertilization

The enhancement of the growth of plants as a result of increased atmospheric CO₂ concentration. Depending on their mechanism of photosynthesis, certain types of plants are more sensitive to changes in atmospheric CO₂ concentration.

Carbon footprint

The total amount of greenhouse gases that are emitted into the atmosphere each year by a person, family, building, organization, or company. A person’s carbon footprint includes greenhouse gas emissions from fuel that an individual burns directly, such as by heating at home or riding in a car. It also includes greenhouse gases that come from producing the goods or services that the individual uses, including emissions from power plants that make electricity, factories that make products, and landfills where trash gets sent.

Carbon sequestration

Terrestrial, or biologic, carbon sequestration is the process by which trees and plants absorb carbon dioxide, release the oxygen, and store the carbon. Geologic sequestration is one step in the process of carbon capture and sequestration (CCS) and involves injecting carbon dioxide deep underground where it stays permanently.

Carbonaceous biochemical oxygen demand (CBOD)

A chemical quantitative measure of the amount of dissolved oxygen required for the biological oxidation of carbon-containing compounds in a sample.

Carpenter bee (Xylocopa micans)

They are considered to be household pests in porch posts, barn beams, and other wooden structures. Both males and females overwinter as adults in nests constructed in wooden materials.

Cationic polymer (or cationic polyelectrolyte)

A positively charged electrolyte used as a coagulant to aid in separating (settling or floating) solids in water or wastewater.

Cationic surfactant

(a) A positively charged surface active agent that lowers the surface tension in water, and can be used as a collector in a flotation process, or as an organic disinfectant in personal cleaners, swimming pools, house roofs, restaurants, etc. (b) an organic quaternary ammonia compound with positively charged surface active moieties.

Cavitation

The formation and collapse of a gas pocket or bubble on the blade of an impeller or the gate of a valve. The collapse of this gas pocket or bubble drives water into the impeller or gate with a terrific force that can cause pitting on the impeller or gate surface. Cavitation is accompanied by loud noises that sound like someone is pounding on the impeller or gate with a hammer.

Centrate

Dilute effluent stream from a centrifuge.

Centrifuge

(a) It is a water-solid separation device that separates the solids from liquid by centrifugal force. Centrifuges are used for separating liquids of different density, thickening slurries, or dewatering solids. (b) It is a mechanical device that uses centrifugal or rotational forces to separate solids from liquids.

Centrifuge thickening

It is sludge preliminary concentration process before sludge watering process involving the use of centrifugal force. Water in a wet dilute sludge is forced out of the wet sludge placed in the spinning drum of a centrifuge.

Centrifuge, basket centrifuge for sludge thickening/dewatering

They are suitable for small plants. It is a semibatch type operation. Sludge cake is collected on the sides of the spinning bowl while the centrate (dilute effluent stream from the centrifuge) overflows the bowl rim. Once solids have built up to a maximum thickness, the feed sludge is stopped and scrapper blades peel the sludge from the walls. The process is then resumed.

Centrifuge, solids bowl centrifuge for sludge thickening/dewatering

Sludge is fed at a constant flowrate into the rotating bowl where it is separated into a dense cake and a dilute stream called centrate. The centrifuge units can be used with no prior chemical conditioning, but solids caputer and centrate quality are improved considerably when the sludge is conditioned with polymer.

Ceramic matrices

Materials like clay that can be converted to ceramics after high temperature treatment.

Characteristic Wastes

In the USA, characteristic wastes may be regulated for exhibiting one of the four characteristics (ignitability, corrosivity, reactivity, and toxicity) of the waste as determined by the US Environmental Protection Agency (USEPA).

Chemical engineering

It is a branch of engineering that uses principles of chemistry, physics, mathematics, biology, and economics to efficiently use, produce, design, transport, and transform energy and materials. The work of chemical engineers can range from the utilization of nanotechnology and nanomaterials in the laboratory to large-scale industrial processes that convert chemicals, raw materials, living cells, microorganisms, and energy into useful forms and products.

Chemical analysis

The use of a standard chemical analytical procedures to determine the concentration of a specific analyte in a sample, or qualitatively or quantitatively measure a specific parameter of a sample.

Chemical oxygen demand (COD)

An environmental chemical test used to measure indirectly organic compounds in water or wastewater.

Childproofing

Making the physical environment safe for the children in your care to reduce the risks of injury.

Chlorination

(a) The application of chlorine to water or wastewater, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results, and (b) one of disinfection processes involving the use of chlorine gas. Disinfection with chlorine is accomplished by adding chlorine gas to the water or wastewater. Sometimes application of sodium hypochlorite (liquid) for disinfection is also called chlorination. Academically disinfection using sodium hypochlorite should be called hypochlorination.

Chlorine demand

Chlorine demand is the difference between the amount of chorine added to wastewater and the amount of residual chlorine remaining after a given contact time. Chlorine demand may change with dosage, time, temperature, pH, or nature or amount of the impurities in the water. Chlorine demand, mg/L = chlorine applied, mg/L – chlorine residual, mg/L

Chlorine requirement

The amount of chlorine that is needed for a particular purpose. Some reasons for adding chlorine are reducing the number of coliform bacteria (Most Probable Number), obtaining a particular chlorine residual, or oxidizing some substance in the water. In each case, a definite dosage of chlorine will be necessary. This dosage is the chlorine requirement.

Chlorine sponge

Incomplete nitrification resulting in excess nitrite levels that react with chlorine. Also known as “Nitrite Lock.”

Chlorofluorocarbons

Gases covered under the 1987 Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone. These gases are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol. All these substances are also greenhouse gases.

Chloroform

It is a colorless, volatile, sweet-smelling liquid (CHCl₃) used as an organic solvent in an analytical procedure and formerly as a general anesthetic in a medical procedure.

Civil engineering

It is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewerage systems, pipelines, structural components of buildings, and railways. Civil engineering is traditionally broken into a number of subdisciplines. It is considered the second-oldest engineering discipline after military engineering, and it is defined to distinguish nonmilitary engineering from military engineering. Civil engineering takes place in the public sector from municipal through to national governments, and in the private sector from individual homeowners through to international companies.

Clari-DAF

It is rectangular dissolved air flotation (DAF) clarifier commercially available from Xylem Water and Wastewater, Zelienople, PA 16063, USA.

Clarifier, settling tank, sedimentation basin

A tank or basin in which water or wastewater is held for a period of time during which most of the heavier solids settle to the bottom and small amount of the lighter material will float to the water surface.

Clarifier, flotation tank

A tank in which water or wastewater is held for a period of time during which most of the lighter air-TSS flocs float to the water surface and small amount of the heavier solids will settle to the tank bottom.

Clean sample

A sample of a natural or synthetic matrix containing no detectable amount of the analyte of interest and no interfering material.

Climate

Climate in a narrow sense is usually defined as the “average weather,” or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands of years. The classical period is 3 decades, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.

Climate change

Climate change refers to any significant change in the measures of climate lasting for an extended period of time. In other words, climate change includes major changes in temperature, precipitation, or wind patterns, among others, that occur over several decades or longer.

Climate feedback

A process that acts to amplify or reduce direct warming or cooling effects.

Climate lag

The delay that occurs in climate change as a result of some factor that changes only very slowly. For example, the effects of releasing more carbon dioxide into the atmosphere occur gradually over time because the ocean takes a long time to warm up in response to a change in radiation.

Climate model

A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive.

Climate sensitivity

In Intergovernmental Panel on Climate Change (IPCC) reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO₂ concentration. More generally, equilibrium climate sensitivity refers to the equilibrium change in surface air temperature following a unit change in radiative forcing (degrees Celsius, per watts per square meter). One method of evaluating the equilibrium climate sensitivity requires very long simulations with Coupled General Circulation Models (Climate model). The effective climate sensitivity is a related measure that circumvents this requirement. It is evaluated from model output for evolving nonequilibrium conditions. It is a measure of the strengths of the feedbacks at a particular time and may vary with forcing history and climate state.

Climate system (or Earth system)

The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations.

Coagulant

(a) A chemical (alum or iron salts) added to water to destabilize particles, allowing subsequent floc formation and removal by clarification (flotation or sedimentation) and/or filtration. (b) Chemicals that cause very fine particles to clump (floc) together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.

Coagulation

(a) The clumping together of very fine particles into large particles (floc) caused by the use of chemicals (coagulants); (b) A process of destabilizing charges of suspended and colloidal particles in water by adding chemicals (coagulants). In coagulation process, positively charged chemicals are added to neutralize or destabilize these negative charges and allow the neutralized particles to accumulate and be removed by clarification (flotation or sedimentation) and/or filtration.

Coal mine methane

Coal mine methane is the subset of coalbed methane that is released from the coal seams during the process of coal mining.

Coalbed methane

Coalbed methane is methane contained in coal seams, and is often referred to as virgin coalbed methane, or coal seam gas.

Cobenefit

The benefits of policies that are implemented for various reasons at the same time including climate change mitigation acknowledging that most policies designed to address greenhouse gas mitigation also have other, often at least equally important, rationales (e.g., related to objectives of development, sustainability, and equity).

Coliform

A type of bacteria. The presence of coliform-group bacteria is an indication of possible pathogenic bacterial contamination. The human intestinal tract is one of the main habitats of coliform bacteria. They may also be found in the intestinal tracts of warm-blooded animals, and in plants, soil, air, and the aquatic environment. Fecal coliforms are those coliforms found in the feces of various warm-blooded animals, whereas the term “coliform” also includes various other environmental sources.

Collector

A device or system designed to collect filter backwash water, or other treatment unit.

Colony

It is a gathering of all the worker bees, drones, queen, and developing brood living together in one hive or other dwelling.

Colorimetric measurement

A means of measuring unknown chemical concentrations in water by measuring a sample’s color intensity. The specific color of the sample, developed by addition of chemical reagents, is measured with a photoelectric colorimeter or is compared with “color standards” using, or corresponding with, known concentrations of the chemical.

Comminuting

It is a grinding or shredding operation for reducing the particle size of objects or debris in the influent wastewater. They are installed with a screen directly in the influent wastewater flow’s channel, with the shredded particles returned to the flow downstream of the screen. The influent flow is channeled to and through these units. The debris is collected against the screen, or outside drum, and the teeth, which penetrate this screen cut up the solids. When the solids are reduced to the size of the screen or drum openings, they pass through and on for additional downstream wastewater treatment. The barminutor is a comminuting device that incorporates revolving cutters that move up and down the upstream face of a bar screen, shredding and cutting whatever debris has accumulated against the screen. The screenings are transported to the cutting device, shredded, and then allowed to fall back into the influent channel downstream of the bar screen.

Comminutor

A device used to reduce the size of the solid chunks in wastewater by shredding (comminuting). The shredding action is like many scissors cutting or chopping to shreds all the large influent solids material in the wastewater.

Community Emergency Response Team (CERT)

A program that educates people about disaster preparedness and provides training in basic disaster response skills.

Complete mix activated sludge process

It is an activated process, in which aeration tank (with about 3–5 hours DT) is usually circular and the influent wastewater and the mixed liquor are completely mixed during aeration operation. It is most useful for treating wastewater with fluctuating organic strength, because it is least susceptible to shock loads among all activated sludge processes. A mechanically stirred reactor best simulates a complete mix condition. When diffused aeration in a rectangular aeration tank is used, the mixture of wastewater influent and the return sludge should enter the aeration tank at several points in a central location with the effluent going into channels on the sides of the aeration tank.

Complex

A substance consisting of many different and connected parts.

Composite

A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a 24-hour time span. Each individual sample is combined with the others in proportion to the rate of flow when the sample was collected. The resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the sample period.

Compost

It is decayed organic material used as a plant fertilizer.

Composting

It is an aerobic biological process designed to reduce organic concentrations, reclaim nutrients, and eliminate pathogenic organisms in the waste sludge or solid wastes. There are at least three major types of composting systems: (a) aerated static pile composting system; (b) windrow composting system; and (c) the in-vessel composting system. Sludge, wood chips leaves, etc., that have been composted properly is a sanitary, nuisance-free, humus-like material. The end product can be used as a soil additive or landfill cover component.

Composting latrine

It is a type of dry (not using water) latrine, which treats human excreta using a biological process called composting, which decomposes excreta and organic matter into a compost-like material but does not destroy all pathogens.

Composting, aerated static pile system

The aerated stack pile consists of a grid of aeration or exhaust piping underlying a mixture of dewatered sludge or small solid wastes (such as leaves, wood chips, waste foods) and bulking agent. Material is composted for 21–28 days and then cured for another 30 days or longer.

Composting, in-vessel system

In this in-vessel system, composting of sludge, solid wastes, and bulking agent is accomplished inside an enclosed container or vessel. Mechanical devices are designed to minimize odors and process time by controlling environmental conditions such as air flow, temperature, and oxygen concentration. There are two types: (a) the plug flow system and (b) the dynamic system.

Composting, windrow system

This composting system is similar to the aerated static pile system. Piles of dewatered sludge, small solids wastes, and bulking agent are periodically turned for aeration and temperature control. The major drawback to this system is that turning the windrows is often accompanied by the release of offensive odors.

Comprehensive Preparedness Guide (CPG) 101

A document designed to provide guidance for developing emergency operations plans. It promotes a common understanding of the fundamentals of risk-informed planning and decision-making to help planners examine a hazard or threat and produce integrated, coordinated, and synchronized plans. The goal of CPG 101 is to assist in making the planning process routine across all phases of emergency management and for all homeland security mission areas. It helps planners at all levels of government in their efforts to develop and maintain viable, all-hazards, all-threats emergency plans.

Computer-aided design (CAD)

It is an automated system for the design, drafting, and display of graphically oriented information.

Concentration

(a) Amount of a chemical in a particular volume or weight of air, water, soil, or other medium; (b) in solutions, the mass, volume, or number of moles of solute present in proportion to the amount of solvent or total solution. Common measures are: molarity, normality, percent, molality, and by specific gravity scales.

Concept of operations (CONOPS)

A component of the basic plan that clarifies the childcare site’s or school’s overall approach to an emergency (i.e., what should happen, when, and at whose direction) and identifies specialized response teams and/or unique resources needed to respond to an incident.

Confined space

Confined space means a space that (a) is large enough and so configured that an employee can bodily enter and perform assigned work; and (b) has limited or restricted means for entry or exit; and (c) is not designed for continuous employee occupancy.

Contact stabilization process

It is a modification of the activated sludge process. In this modification, the adsorptive capacity of the floc is utilized in the contact tank to adsorb suspended, colloidal, and some dissolved organics. The hydraulic detention time in the contact tank is only about 30–60 minutes (based on average daily flow). After the biological sludge is separated from the wastewater in the secondary clarifier (either secondary sedimentation clarifier, or secondary flotation clarifier), the concentrated sludge is separately aerated in the stabilization tank with a detention time of 2 to 6 hours (based on sludge recycle flow). The adsorbed organics undergo oxidation in the stabilization tank and are synthesized into microbial cells. If the detention time is long enough in the stabilization tank, endogenous respiration will occur, along with a concomitant decrease in excess biological sludge production. Following stabilization, the reaerated sludge is mixed with incoming wastewater in the contact tank and the cycle starts anew. Volatile compounds are driven off to a certain extent by aeration in the contact and stabilization tanks. Metals will also be partially removed, with accumulation in the sludge. This process requires smaller total aeration volume than the conventional activated sludge process. It also can handle greater organic shock and toxic loadings because of the biological buffering capacity of the stabilization tank and the fact that at any given time. The majority of the activated sludge is isolated from the main stream of the plant flow. Generally, the total aeration basin volume (contact basin plus stabilization basin) is only 50–75 percent of that required in the conventional activated sludge system. An equalization basin is generally recommended for equalizing the wastewater influent flow.

Contamination

A general term signifying the introduction into water of microorganisms, chemicals, wastes, or sewage, which renders the water unfit for its intended use.

Conventional biological wastewater treatment system

It normally includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber, etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary sedimentation clarification for removing mainly total suspended solids from preliminary effluent, (c) secondary biological treatment units (such as activated sludge aeration or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent discharge standards.

Conventional physicochemical wastewater treatment system

It normally includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber, etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary sedimentation clarification for removing mainly total suspended solids from preliminary effluent, (c) secondary physicochemical treatment units (such as chemical precipitation/coagulation or equivalent plus secondary sedimentation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent discharge standards. In the nitrification and denitrification steps, only tertiary sedimentation clarification will be used for solid-water separation.

Cooling

It is a thermodynamic process to lower the temperature.

Cooling range

The temperature difference between hot water entering the tower and cooled water exiting the tower.

Coordinate

It is an x,y location in a Cartesian coordinate system or an x,y,z coordinate in a three-dimensional system. Coordinates represent locations on the Earth’s surface relative to other locations.

Coral bleaching

The process in which a coral colony, under environmental stress, expels the microscopic algae (zooxanthellae) that live in symbiosis with their host organisms (polyps). The affected coral colony appears whitened.

Corrosivity

Any substance, which exhibits any of the following properties, is considered a hazardous waste due to corrosivity: (a) an aqueous material with pH less than or equal to 2 or greater than or equal to 12.5; and (b) a liquid that corrodes steel at a rate greater than 1/4 inch per year at a temperature of 55 ° C.

Cross connection

A connection between a drinking (potable) water system and an unapproved water supply. For example, if you have a pump moving nonpotable water and hook into the drinking water system to supply water for the pump seal, a cross connection, or mixing, between the two water systems can occur. This mixing may lead to contamination of the drinking water.

Cryosphere

One of the interrelated components of the Earth’s system, the cryosphere, is frozen water in the form of snow, permanently frozen ground (permafrost), floating ice, and glaciers. Fluctuations in the volume of the cryosphere cause changes in ocean sea level, which directly impact the atmosphere and biosphere.

CSHO

It is an abbreviation for an OSHA Compliance Safety and Health Officer.

Cuckoo bee (Epeolus compactus)

They are parasitic bees of wild species, not affecting humans. They lack pollen-carrying baskets or brushes. So they are parasitic, usually on species of bees of the genus Colletes.

Cutter

It describes the type of excavator head such as a basket cutterhead, plain-edge cutter, or bucketwheel, which houses the suction intake and is used for cutting or agitating the materials being dredged.

DAF

Dissolved air flotation process.

DAFF

Dissolved air flotation and filtration.

Data

Facts or figures from which conclusions can be inferred.

Database

It is a logical collection of interrelated information, managed and stored as a unit. A GIS database includes data about the spatial location and shape of geographic features recorded as points, lines, and polygons as well as their attributes.

Debris flow

Another term for a landslide or mudslide. See landslide definition.

Dechlorination

It is a process for removal of excess amount of residual chlorine in a chlorination disinfection process. Dechlorination is accomplished by using a reducing chemical such as sulfur dioxide (gas), sodium bisulfate (liquid), or sodium metabisulfite (liquid).

Dechlorination

The removal of chlorine from the effluent of a treatment plant.

Deforestation

Those practices or processes that result in the conversion of forested lands for nonforest uses. Deforestation contributes to increasing carbon dioxide concentrations for two reasons: 1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present.

Denitrification filter

It is an attached-growth biological process filter using wood, plastic, rock, granular activated carbon, or sand as filtration media for denitrification (conversion of nitrate to nitrogen gas) of wastewater under anoxic/anaerobic condition.

Denitrification followed by flotation clarification

The process involves the reduction of nitrates and nitrites to nitrogen gas through the action of facultative heterotrophic bacteria. In suspended-growth separate stage denitrification processes, nitrified wastewater containing primarily nitrates is passed through a mixed anaerobic vessel containing denitrifying bacteria. Since the nitrified feed-water contains very little carbonaceous materials, a supplemental source of carbon (such as methanol, sugar, acetic acid, ethanol, or other compounds) is required to maintain the denitrifying biomass. This supplemental energy is provided by feeding methanol, for instance, to the biological reactor along with the nitrified wastewater. Mixing in the anaerobic denitrification reaction vessel may be accomplished using low-speed paddles analogous to standard flocculation equipment. Flotation clarification follows the denitrification step with the floated sludge being either returned to the head end of the denitrification system or wasted. An intermediate aeration step for stabilization (much less than 40 minutes) may be needed to guard against carryover of carbonaceous materials. The denitrification reactor may be covered but not airtight to assure anaerobic conditions.

Denitrification followed by membrane clarification

Same as “denitrification followed by flotation clarification” except that the flotation clarification is replaced by a membrane filtration reactor.

Denitrification followed by sedimentation clarification

The process involves the reduction of nitrates and nitrites to nitrogen gas through the action of facultative heterotrophic bacteria. In suspended-growth separate stage denitrification processes, nitrified wastewater containing primarily nitrates is passed through a mixed anaerobic vessel containing denitrifying bacteria. Since the nitrified feed-water contains very little carbonaceous materials, a supplemental source of carbon (such as methanol, sugar, acetic acid, ethanol, or other compounds) is required to maintain the denitrifying biomass. This supplemental energy is provided by feeding methanol, for instance, to the biological reactor along with the nitrified wastewater. Mixing in the anaerobic denitrification reaction vessel may be accomplished using low-speed paddles analogous to standard flocculation equipment. Following the reactor, the denitrified effluent is aerated for a short period (5 to 10 minutes) to strip out gaseous nitrogen formed in the previous step, which might otherwise inhibit sludge settling. Sedimentation clarification follows the gas-stripping step with the collected sludge being either returned to the head end of the denitrification system, or wasted. An intermediate aeration step for stabilization (about 50 minutes) between the denitrification reactor and the stripping step may be used to guard against carryover of carbonaceous materials. The denitrification reactor may be covered but not airtight to assure anaerobic conditions.

Denitrification

(a) The anoxic biological reduction of nitrate-nitrogen to nitrogen gas. (b) The removal of some nitrogen from a system. (c) An anoxic process that occurs when nitrite or nitrate ions are reduced to nitrogen gas and nitrogen bubbles are formed as a result of this process. (d) The biochemical reduction reaction of reducing nitrate-nitrogen to nitrogen gas in an anoxic environment.

Derived-From Wastes

USEPA’s “derived-from” rule regulates any solid waste generated from the treatment, storage, or disposal of a hazardous waste, including any sludge, spill residue, ash, emission control dust, or leachate (but not including precipitation run-off) is a hazardous waste under 40 CFR 261.4(c)(2)(i), with some specified exclusions.

Desertification

Land degradation in arid, semiarid, and dry subhumid areas resulting from various factors, including climatic variations and human activities. Further, the UNCCD (The United Nations Convention to Combat Desertification) defines land degradation as a reduction or loss, in arid, semiarid, and dry subhumid areas, of the biological or economic productivity and complexity of rain-fed cropland, irrigated cropland, or range, pasture, forest, and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns, such as (i) soil erosion caused by wind and/or water; (ii) deterioration of the physical, chemical, and biological or economic properties of soil; and (iii) long-term loss of natural vegetation. Conversion of forest to nonforest.

Detention time

The time required to fill a tank at a given flow or the theoretical time required for a given flow of wastewater to pass through a tank.

Detoxification

The act of detoxifying.

Detritus

The heavy, coarse mixture of grit and organic material carried by wastewater (also called grit).

Diffused-air aeration

A diffused air activated sludge plant takes air, compresses it, and then discharges the air below the water surface of the aerator through some type of air diffusion device.

Diffuser

A device used to break the air stream from the blower system into fine bubbles in an aeration tank or reactor.

Digester

A tank in which sludge is placed to allow decomposition by microorganisms. Digestion may occur under anaerobic (more common) or aerobic conditions.

Digger bee (Ptilothrix bombiformis)

They are natural bees of wild species, not affecting humans. Adults burrow into the ground where they store a mixture of honey and pollen to be used as larval food. Adults often are seen visiting the flowers of hibiscus.

Digging depth, dredging

It is the maximum design depth from which the dredge can excavate material, which is usually stated as a measurement from water level and typically expressed in feet or meters.

Digital Elevation Model (DEM)

It is a terrain elevation data provided in digital form.

Digitize

It is an action to encode map features as x,y coordinates in digital form. Lines are traced to define their shapes. This can be accomplished either manually or by use of a scanner.

Disinfection

Potable water disinfection is used in an attempt to destroy all pathogenic agents in drinking water for public health protection. Wastewater disinfection is used in an attempt to destroy pathogenic agents in a wastewater stream and protect the best uses of the receiving stream or groundwater. Environmental disinfection is used in an attempt to destroy pathogenic agents in rooms, houses, swimming pools, buildings, restaurants, streets, parks, etc., to prevent the spread of pathogenic agents, such as pathogenic bacteria and Coronavirus in the environment. Typical disinfection techniques used include chlorine (gas), sodium hypochlorite (liquid), bromine (gas), bromine dioxide (gas), UV (light), ozone (gas), and cationic surfactant (water-soluble solid).

Disinfection

The process designed to kill or inactivate most microorganisms in wastewater, including essentially all pathogenic (disease-causing) bacteria. There are several ways to disinfect, with chlorination being the most frequently used in water and wastewater treatment plants.

Dispersion

A uniform and maximum separation of extremely fine particles, often of colloidal size.

Dissolved air flotation (DAF)

One of dissolved gas flotation (DGF) processes when air is used for generation of gas bubbles. See dissolved gas flotation (DGF).

Dissolved gas flotation (DGF)

It is a process involving pressurization of gas at 25 to 95 psig for dissolving gas into water, and subsequent release of pressure (to one atm) under laminar flow hydraulic conditions for generating extremely fine gas bubbles (20–80 microns), which become attached to the impurities to be removed and rise to the water surface together. The impurities or pollutants to be removed are on the water surface and are called float or scum, which are scooped off by sludge collection means. The clarified water is discharged from the flotation clarifier’s bottom. The gas flow rate is about one percent of influent liquid flow rate. The attachment of gas bubbles to the impurities can be a result of physical entrapment, electrochemical attraction, surface adsorption, and/or gas stripping. The specific gravity of the bubble-impurity agglomerate is less than 1, resulting in buoyancy or nonselective flotation (i.e., Save-All).

Dissolved oxygen (DO)

Molecular (atmospheric) oxygen dissolved in water or wastewater.

Distilled water

Water that has been purified by distillation (boiling the water off as steam and condensing it back to a liquid, leaving the impurities behind). Having been boiled, it is also sterile.

Dredge mining

It is a practical means for extracting submerged sand, gravel, sand, iron ore, coal, fine tailings, and other minerals. Mining with a dredge is an efficient way to obtain materials and hydrotransport them to on-shore processing facilities, whether it be sand, gravel, or hard salt deposits.

Dredge pump

It is a horizontal centrifugal pump designed to handle abrasive granular materials and solids of limited size in suspension. They are distinct from water and slurry pumps, which carry liquid and homogeneous mixtures, respectively.

Dredge

It is a piece of machinery used for removing materials that have been partially or fully immersed under water, with the intent of collecting the sediment and redistributing the content at a separate location.

Dredger

It is the European term to describe a dredge.

Dredging

It describes the digging or mining action used to collect sediment from below the water surface. The gathered sediment is then either transported elsewhere or repurposed for other uses.

Drift eliminators

Baffles, or other specialized collection products, placed in the air exit path to capture water droplets. (Note: as per the previous mention of scrubbing, again, mist elimination in scrubbing is a similar application.)

Drift

Also known as windage, small droplets of water, which are carried out of the tower by the airflow, normally expressed as a % of total water flow rate.

Drill

A type of exercise that is a coordinated, supervised activity usually employed to test a single specific operation or function in a single agency. Drills are commonly used to provide training on new equipment, develop or test new policies or procedures, or practice and maintain current skills.

Drone bee

It is the sexually active male honey bee. Drones are most numerous during the summer, but as food becomes scarce, the worker bees kill the drones and remove them from the hive. A drone bee can only mate the female queen bee once, and then die.

Dry bulb temperature

Air temperature, measured by standard means.

Dryland farming

A technique that uses soil moisture conservation and seed selection to optimize production under dry conditions.

Dual Wheel Excavator (DWE)

It is an Ellicott’s term for its patented underwater bucket wheel excavator, also known as a Wheel Dragon™ excavator.

Earthquake

The sudden movement of the Earth caused by the breaking and shifting of rock beneath the Earth’s surface.

Eccentricity

The extent to which the Earth’s orbit around the Sun departs from a perfect circle.

Ecology

It is a branch of biology that deals with the mutual relations between organisms and their environment. Ecology implies more the webs of natural forces and organisms, their competition and cooperation, and how they live off one another.

Ecosystem

Any natural unit or entity including living and nonliving parts that interact to produce a stable system through cyclic exchange of materials.

Effluent

Wastewater or other liquid—raw (untreated), partially or completely treated—flowing from a reservoir, basin, treatment process, or treatment plant.

Elutriation

The washing of digested sludge with fresh water, plant effluent, or other wastewater. The goal is to remove fine particles and/or the alkalinity in the sludge. This process reduces the demand for conditioning chemicals and improves settling or filtering characteristics of the sludge.

Emergency action plan

A simple set of emergency procedures that includes, at a minimum, parent/guardian contact information; medical information for each child; emergency services contact information; how to accommodate the needs of each child; and procedures for shelter-in-place, evacuation, and reunification.

Emergency kit

Items to help you survive during and after an emergency, including food, water, and other supplies.

Emergency operations plan

A comprehensive formal plan based on the Federal Emergency Management Agency’s (FEMA’s) Comprehensive Preparedness Guide (CPG) steps. It describes how people and property will be protected; details who is responsible for carrying out specific actions; identifies the personnel, equipment, facilities, supplies, and other resources available; and outlines how all actions will be coordinated.

Emissions

The release of a substance (usually a gas when referring to the subject of climate change) into the atmosphere.

Emissions factor

A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g., grams of carbon dioxide emitted per barrel of fossil fuel consumed, or per pound of product produced).

Emotional and psychological recovery

Identification of strategies to address disruption of services, psychological injury, and external pressure.

Endocrine-disrupting compounds (EDCs)

They are chemicals that mimic endogenous hormones, interfere with pharmacokinetics, or act by other mechanisms. Such adverse effects as compromised reproductive fitness, functional or morphological birth defects, cancer, and altered immune functions, among others, have been reported.

Endocrine disruptors

(a) They are substances that are not produced in the body but act by mimicking or antagonizing natural hormones and are mostly man-made found in various materials. By interfering with the human body’s endocrine system, endocrine disruptors produce adverse developmental, reproductive, neurological, and immune effects in humans, abnormal growth patterns and neurodevelopmental delays in children. (b) They are chemicals that mimic endogenous hormones, interfere with pharmacokinetics, or act by other mechanisms resulting in adverse effects such as compromised reproductive fitness, functional or morphological birth defects, cancer, and altered immune functions. (c) They are environmental pollutants with adverse hormonal effects on wildlife and humans, such as pesticides (methoxychlor), surfactants (nonylphenol), plasticizers (diethylphthalate), and organohalogens (polychlorinated biphenyls or PCBs and dioxin).

Endocrine systems

They are also referred to as hormone systems and are found in all mammals, birds, fish, and many other types. The endocrine system regulates all biological processes in the body from conception through adulthood and into old age, including the development of the brain and nervous system, the growth and function of the reproductive system, as well as the metabolism and blood sugar levels.

Energy efficiency

Using less energy to provide the same service.

ENERGY STAR

A US Environmental Protection Agency voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency.

Energy

(a) In engineering physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. (b) Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. (c) Energy is the power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines.

Engineering

It is a professional field involving the use of science and mathematics to invent, create, design, develop, or improve technologies.

Engineers Without Borders: USA

It is a nonprofit organization established to partner with developing communities in order to improve their quality of life.

Enhanced biological phosphorus removal (EBPR)

The process of phosphorus removal in wastewater that relies on the proliferation and selection of a microbiological population capable of storing phosphorus in excess of their normal growth requirements. Also called biological nutrient removal (BNR).

Enhanced greenhouse effect

The concept that the natural greenhouse effect has been enhanced by increased atmospheric concentrations of greenhouse gases (such as CO₂ and methane) emitted as a result of human activities. These added greenhouse gases cause the Earth to warm.

Enteric fermentation

Livestock, especially cattle, produce methane as part of their digestion. This process is called enteric fermentation, and it represents one-third of the emissions from the agriculture sector.

Environmental engineering

It is a professional engineering discipline that takes from broad scientific topics like chemistry, biology, ecology, geology, hydraulics, hydrology, microbiology, and mathematics to create solutions that will protect and also improve the health of living organisms and improve the quality of the environment. Environmental engineering is a subdiscipline of civil engineering, chemical engineering, and mechanical engineering.

Environmental remediation

(a) It is a means of dredging that is beneficial to both recreational users and natural wildlife habitats. The natural flow of sediments and industrial runoff can often choke off channels that feed fresh water to inland wetlands or ponds. Dredging these channels allows water to circulate in and out of these inland sites, bringing in nutrients and flushing out waste. (b) It is an action of pollution control that is beneficial to both people and ecological system.

Environmental resource management

It is the management of the interaction and impact of human societies on the environment. It is not, as the phrase might suggest, the management of the environment itself. Environmental resources management aims to ensure that ecosystem services are protected and maintained for future human generations, and also maintain ecosystem integrity through considering ethical, economic, and scientific (ecological) variables. Environmental resource management tries to identify factors affected by conflicts that arise between meeting needs and protecting resources. It is thus linked to environmental protection, sustainability, and integrated landscape management.

Environmental risk management

The conscious and coordinated effort in appraising the potential and/or existing impact of various productive activities on their environment and people.

Environmental science

It is an interdisciplinary academic field that integrates physical, biological, and information sciences (including ecology, biology, chemistry, mathematics, microbiology, geology, information science, etc.)

Environmental studies

It is a multidisciplinary academic field, which systematically studies human interaction with the environment in the interests solving complex problems. Environmental studies brings together the principles of the physical sciences, commerce/economics, and social sciences so as to solve contemporary environmental problems. It is a broad field of study that includes the natural environment, the built environment, and the sets of relationships between them. The field encompasses study in basic principles of ecology and environmental science, as well as associated subjects such as ethics, geography, anthropology, policy, politics, urban-planning, law, economics, philosophy, sociology and social justice, planning, pollution control, and natural resource management. There are also many degree programs in Environmental Studies including a Master’s degree and a Bachelor’s degree.

Environmental technology

It may include (envirotech), green technology (greentech), or clean technology (cleantech). It is the application of one or more of environmental science, green chemistry, environmental monitoring, and electronic devices to monitor, model, and conserve the natural environment and resources, and to curb the negative impacts of human involvement. The term is also used to describe sustainable energy generation technologies such as photovoltaics, wind turbines, bioreactors, etc. Sustainable development is the core of environmental technologies. The term environmental technologies is also used to describe a class of electronic devices that can promote sustainable management of resources.

Equalization basin

A holding basin in which variations in flow and composition of a liquid are averaged. Such basins are used to provide a flow of reasonably uniform volume and composition to a treatment unit. Also called a balancing reservoir.

Estuary

Body of water that is located at the lower end of a river and is subject to tidal fluctuations.

Eutrophication

(a) Nutrient overenrichment of a body of water, causing increased growth of algae and rooted aquatic plants. (b) Overenrichment of a water body with nutrients, resulting in excessive growth of organisms and depletion of oxygen concentration. (c) The increase of nutrient levels of a lake or other body of water; this usually causes an increase in the growth of aquatic animal and plant life.

Evacuation

The organized, phased, and supervised withdrawal, dispersal, or removal of children, personnel, and visitors from dangerous or potentially dangerous areas.

Evaporation

The process by which water changes from a liquid to a gas or vapor.

Evapotranspiration

(a) The combined process of evaporation from the Earth’s surface and transpiration from vegetation. (b) The process by which water vapor passes into the atmosphere from living plants, also called transpiration. (c) The total water removed from an area by transpiration (living plants) and by evaporation from soil, snow, and water surfaces.

Excessive heat

When heat index values meet or exceed daytime highs of 105–110 ° F (depending on local climate).

Excreta

It is a waste matter discharged from the body, especially feces and urine.

Exercise

A way to train for, assess, practice, and improve performance in prevention, protection, response, and recovery capabilities in a risk-free environment. Exercises can be used for testing and validating policies, plans, procedures, training, equipment, and interagency agreements; clarifying and training personnel in roles and responsibilities; improving interagency coordination and communications; identifying gaps in resources; improving individual performance; and identifying opportunities for improvement.

Extended aeration activated sludge process

A long aeration time (over 18 hours DT) is employed in an extended aeration system. It is applicable only to small wastewater treatment plants of less than 3785 m³/day or 1.0 MGD. Normally, no primary clarifier is provided and no exercise of optimum return sludge control is attempted although the return activated sludge (RAS) flow is about 75% to 100% of plant flow. The objective is to simplify the process both in construction and in operation. Sludge production is very small because of prolonged endogenous oxidation, which minimizes the problem of sludge treatment and disposal. The aeration effluent’s sludge normally has an inferior settling characteristic. Therefore, a secondary flotation clarifier is better for an extended aeration plant.

Fallow

It is an area (of farmland) plowed and harrowed but left unsown for a period in order to restore its fertility as part of a crop rotation or to avoid surplus production

F-Cell

Dissolved air flotation cell or DAF.

Feedback mechanisms

Factors that increase or amplify (positive feedback) or decrease (negative feedback) the rate of a process. An example of positive climatic feedback is the ice-albedo feedback.

FEMA

The Federal Emergency Management Agency is the USA’s lead emergency management and preparedness agency.

Fermentation

The process in which bacteria degrade organic matter under anaerobic conditions, such as in a collection system, primary clarifier, anaerobic selector, or fermenter tank

FF-Cell

Dissolved air flotation and filtration cell or DAFF.

Field margins

It is generally the least productive areas of a field and just a 1-metre grass strip between the outer edge of the hedges, and the crop edge can benefit wildlife in many ways.

Filamentous organism

(a) Microorganisms, such as bacterial, algal, or fungal species, that grow in thread-like colonies, or a biological mass that may interfere with settling in clarifiers, or may interfere with drainage through a filter. (b) Organisms that grow in a thread or filamentous form. Common types are Thiothrix and Actinomycetes. A common cause of sludge bulking in the activated sludge process.

Filtration

It is usually a granular medial filtration process, which involves the passage of wastewater or water through a bed of filter media with resulting deposition of suspended solids. Eventually the pressure drop across the bed becomes excessive or the ability of the bed to remove suspended solids is impaired. Cleaning is then necessary to restore operating head and effluent quality. The time in service between cleanings is termed the filter run time or run length. The head loss at which filtration is interrupted for cleaning is called the terminal head loss, and this head loss is maximized by the judicious choice of media sizes. Dual media filtration involves the use of both sand and anthracite as filter media, with anthracite being placed on top of the sand. Gravity filters operate by either using the available head from the previous treatment unit, or by pumping to a flow split box after which the wastewater flows by gravity to the filter cells. Pressure filters utilize pumping to increase the available head. A filter unit generally consists of a containing vessel, the filter media, structures to support the media, distribution and collection devices for filter influent, effluent, and backwash water flows, supplemental cleaning devices, ad necessary controls for flows, water levels, and backwash sequencing. Backwash sequences can include air scour or surface wash steps. Backwash water can be stored separately or in chambers that are integral parts of the filter unit. Backwash water can be pumped through the unit or can be supplied through gravity head tanks.

Fire-resistant material

A material designed to withstand heat and resist burning to aid in saving lives and protecting property.

First responder

Includes organizations and individuals who assume an emergency management role. Also known as emergency management or response personnel.

Floc

(a) Collections of smaller particles that have agglomerated together into larger, more separable, floatable or settleable particles as result of the coagulation process; (b) clumps of bacteria and particles or coagulants and impurities that have come together and formed a cluster. Found in aeration tanks, secondary clarifiers, and chemical precipitation processes.

Flocculation

(a) A water treatment unit process following coagulation that uses gentle stirring to bring suspended particles together so that they will form larger, more separable (floatable or settleable) floc. (b) The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing.

Flocculator

A process device to enhance the formation of floc in a water. Mixing energy can be provided by slow turning mechanical means or head loss.

Flood

A general and temporary condition of partial or complete inundation of normally dry land areas from overflow of inland or tidal waters, unusual or rapid accumulation or runoff of surface waters, or mudslides/mudflows caused by accumulation of water.

Flotation cell

A dissolved air flotation cell or unit process.

Flotation thickening

In a dissolved air flotation (DAF) sludge thickening process, air is introduced into liquid sludge that is being held at an elevated pressure. When the sludge is depressurized, the dissolved air is released as finely divided air bubbles carrying the solids to the top, where they are compacted and removed.

Flotation-filtration cell

A package treatment plant which consists of both dissolved air flotation and filtration unit processes.

Fluidized bed incinerator

In the fluidized bed system, dewatered sludge or small solid waste is fed into a bed of hot sand fluidized by circulating air. There is rapid drying and combustion of the sludge or solid waste. Ash is carried out of the incinerator by the combustion gases and is separated by a wet scrubber system or equivalent.

Fluorinated gases

Powerful synthetic greenhouse gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons) and are often used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. These gases are emitted in small quantities compared to carbon dioxide (CO₂), methane (CH₄), or nitrous oxide (N₂O), but because they are potent greenhouse gases, they are sometimes referred to as high global warming potential gases (high GWP gases).

Fluorocarbons

Carbon-fluorine compounds that often contain other elements such as hydrogen, chlorine, or bromine. Common fluorocarbons include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

Forage

(a) The food supply of an animal; (b) an action (of a person or animal) searching widely for food or provisions.

Force main

A pipe that carries wastewater under pressure from the discharge side of a pump to a point of gravity flow downstream.

Forcing mechanism

A process that alters the energy balance of the climate system, i.e., changes the relative balance between incoming solar radiation and outgoing infrared radiation from Earth. Such mechanisms include changes in solar irradiance, volcanic eruptions, and enhancement of the natural greenhouse effect by emissions of greenhouse gases.

Fossil fuel

A general term for organic materials formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the Earth’s crust over hundreds of millions of years.

Freeboard

The vertical distance from the normal water surface to the top of the confining wall.

Fuel switching

In general, this is substituting one type of fuel for another. In the climate-change discussion, it is implicit that the substituted fuel produces lower carbon emissions per unit energy produced than the original fuel, e.g., natural gas for coal.

Full-scale exercise

A multiagency, multijurisdictional operations-based exercise involving actual deployment of resources in a coordinated response as if a real incident had occurred. A full-scale exercise tests many components of one or more capabilities within emergency response and recovery, and is typically used to assess plans and procedures under crisis conditions, and assess coordinated response under crisis conditions. Characteristics of a full-scale exercise include mobilized units, personnel, and equipment; a stressful, realistic environment; and scripted exercise scenarios.

Functional annex

A component of an emergency operations plan that describes procedures and missions for many hazards.

Functional exercise

A single-agency or multiagency operations-based exercise designed to evaluate capabilities and multiple functions using a simulated response. Characteristics of a functional exercise include simulated deployment of resources and personnel, rapid problem solving, and a highly stressful environment.

Fungicide

It is a chemical that destroys fungus.

General circulation model (GCM)

A global, three-dimensional computer model of the climate system, which can be used to simulate human-induced climate change. GCMs are highly complex and they represent the effects of such factors as reflective and absorptive properties of atmospheric water vapor, greenhouse gas concentrations, clouds, annual and daily solar heating, ocean temperatures and ice boundaries. The most recent GCMs include global representations of the atmosphere, oceans, and land surface.

Geocode

It is a process of identifying a location by one or more attributes from a base layer.

Geographic Information System (GIS)

It is an organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.

Geosphere

The soils, sediments, and rock layers of the Earth’s crust, both continental and beneath the ocean floors.

Glacier

A multiyear surplus accumulation of snowfall in excess of snowmelt on land and resulting in a mass of ice at least 0.1 km2 in area that shows some evidence of movement in response to gravity. A glacier may terminate on land or in water. Glacier ice is the largest reservoir of fresh water on Earth, and second only to the oceans as the largest reservoir of total water. Glaciers are found on every continent except Australia.

Global average temperature

An estimate of Earth’s mean surface air temperature averaged over the entire planet.

Global Positioning System (GPS)

It is a satellite-based device that records x,y,z coordinates and other data. Ground locations are calculated by signals from satellites orbiting the Earth. GPS devices can be taken into the field to record data while walking, driving, or flying.

Global warming potential (GWP)

A measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide.

Global warming

The recent and ongoing global average increase in temperature near the Earth’s surface.

Glycogen-accumulating organisms (GAOs)

They are organisms that take up glycogen and volatile fatty acids during metabolism, sometimes competing with phosphorus-accumulating organisms for food sources.

Glycogen

It is a polysaccharide of glucose, which is energy storage inside a cell. It is present in all cells; however, microorganisms that accumulate glycogen in cells during the anaerobic stage of a bio-P process are not able to perform biological nutrient removal.

Good laboratory practices (GLPs)

General guidelines or formal regulations for performing basic laboratory operations or activities that are known or believed to influence the quality and integrity of the results. The purpose of GLP is for personal protection, laboratory protection, proper chemical storage, and proper waste management.

Grab sample

A single sample of water collected at a particular time and place, which represents the composition of the water only at that time and place.

Grab sample

A single sample which is collected at one point in time and place.

Granular activated carbon adsorption

Granular activated carbon (GAC) is used in wastewater substances. GAC systems generally consist of vessels in which the carbon is placed, forming a “filter” bed. These systems can also include carbon storage vessels and thermal regeneration facilities. Vessels are usually circular for pressure systems or rectangular for gravity flow systems. Once the carbon adsorptive capacity has been fully utilized, it must be disposed of or regenerated. Usually, multiple carbon vessels are used to allow continuous operation. Columns can be operated in series or parallel modes. All vessels must be equipped with carbon removal and loading mechanisms to allow for the removal of spent carbon and the addition of new material. Flow can be either upward or downward through the carbon bed. Vessels are backwashed periodically. Surface wash and air scour systems can also be used as part of the backwash cycle. Small systems usually dispose of spent carbon or regenerate it offsite. Systems above about 3 to 5 MGD (million gallons per day) usually provide on-site regeneration of carbon for economic reasons.

Gravity belt thickening

It is a process for removing water from a wet dilute sludge using a moving belt. Dilute sludge is conditioned with a polymer and fed into a feed/distribution box of a belt thickening device. The sludge distributes evenly on the moving belt as water drains through the porous belt and the thickened sludge is discharged.

Gravity thickening

Its tank design is similar to a conventional sedimentation tank. Dilute sludge is fed to a center feed well. The feed sludge is allowed to settle and compact, and the thickened sludge is withdrawn.

Green solvent

An environmentally friendly solvent, or biosolvents, which may be derived from the processing of agricultural crops, such as corn.

Greenhouse effect

Trapping and build-up of heat in the atmosphere (troposphere) near the Earth’s surface. Some of the heat flowing back toward space from the Earth’s surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the Earth’s surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.

Greenhouse gas (GHG)

Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride.

Grinding

It is a unit operation for reducing the particle size of objects or debris in the influent wastewater, also termed shredding or comminuting. These devices may be installed with a screen directly in the wastewater flow or separately out of the wastewater flow, with the shredded particles returned to the flow downstream of the screen. Only those shredding and grinding devices that are installed directly in the influent channel are termed comminuting devices.

Grit chamber

It is a grit removal device that is designed to allow the settling out of this material. Grit removal is an important process for several reasons: (1) to prevent cementing effects at the bottom of sludge digesters and primary clarification tanks; (2) to reduce the potential for clogging of pipes and sludge hoppers; (3) to protect moving mechanical equipment and pumps from unnecessary wear and abrasion; (4) to reduce accumulations of materials in aeration tanks and sludge digesters, which would result in a loss of usable volume; and (5) to reduce accumulations at the bases of mechanical screens. There are two types of grit chambers. The velocity controlled grit chambers limit the velocity in the rectangular channels to a maximum of 1 foot per second (fps). This velocity is low enough to allow the grit to settle but fast enough to maintain a majority of the organic material in suspension. The aerated grit chambers are normally sized on the basis of both detention time and volume of air. Typically, the detention time is in the range of 2 to 5 minutes, and the air flow is in the range of 0.04 to 0.06 cu ft./ gallon of wastewater. The constant head type of system is normally designed using an overflow rate of 15,000 gallons per day per square foot and a 1 minute detention time at peak day flows.

Grit removal

Grit removal is accomplished by providing an enlarged channel or chamber which causes the flow velocity to be reduced and allows the heavier grit to settle to the bottom of the channel where it can be removed.

Grit

(a) It includes sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, and other large-sized unwanted materials in wastewater. (b) The heavy material present in wastewater, such as sand, coffee grounds, eggshells, gravel, and cinders.

Groundwater

The supply of fresh water found beneath the Earth’s surface (usually in aquifers) which is often accessed through wells and springs.

Habitat fragmentation

A process during which larger areas of habitat are broken into a number of smaller patches of smaller total area, isolated from each other by a matrix of habitats unlike the original habitat.

Halocarbons

Compounds containing either chlorine, bromine, or fluorine and carbon. Such compounds can act as powerful greenhouse gases in the atmosphere. The chlorine- and bromine-containing halocarbons are also involved in the depletion of the ozone layer.

Hazard

A natural, technological, or human-caused source or cause of harm or difficulty.

Hazardous wastes

A hazardous waste is a material that is subject to special consideration by the US Environmental Protection Agency (USEPA), under 40CFR261. State or local authorities may also designate additional materials as hazardous waste in their areas. The definition given by 40 CFR 261 defines a hazardous waste as a solid waste that is not excluded from regulation and meets one or more of the following criteria: (a) it is a discarded commercial chemical product, off-specification species, container residue, or spill residue of materials specifically listed in 40CFR261.33 (P- and U-codes); (b) it is a waste from a specific source listed in 40CFR261.32 (K-code); (c) it is a waste from a non-specific source listed in 40CFR261.31 (F-code); and/or (d) it displays any of the following characteristics of hazardous wastes: ignitability (such as flash point is below 60 ° C or 140 ° F, it is classified by the US Department of Transportation,DOT, as an oxidizer D001), corrosivity (such as the pH of the waste material is less than or equal to 2, or greater than or equal to 12.5, or classified by DOT as D002), reactivity (such as the waste material is unstable, reacts violently with water, may generate toxic gases when mixed with water, or classified by DOT as D003), or toxicity (such as it is classified by DOT ad D004-D043).

Hazard-specific annex

A component of an emergency operations plan that describes strategies for managing specific hazards.

Headloss

It is an indirect measure of loss of energy or pressure of flowing water. It is measured as the difference in elevation between the upstream water surface and the downstream water surface.

Headworks

The facilities where wastewater enters a wastewater treatment plant. The headworks may consist of bar screens, comminutors, a wet well, and pumps.

Heat island

An urban area characterized by temperatures higher than those of the surrounding non-urban area. As urban areas develop, buildings, roads, and other infrastructure replace open land and vegetation. These surfaces absorb more solar energy, which can create higher temperatures in urban areas.

Heat load

Amount of heat exchanged within the tower between water and air, expressed per unit of time. It can also be expressed as the product of the quantity of water circulated within the tower per unit time and the cooling range.

Heat waves

A prolonged period of excessive heat, often combined with excessive humidity.

Heavy metal

A general term, which applies to the group of metals and metalloids, and it has an atomic density more prominent than 4000 kg/m³.

Herbicide

It is a substance that is toxic to plants and is used to destroy unwanted vegetation.

Heterotrophic

Microorganisms that use organic matter (carbon) for energy and growth and can grow in both aerobic and anoxic environments using both dissolved and chemically bound oxygen (nitrates)

Hive

It is the structure used by bees for a home.

Honey bees (Apis mellifera)

They are completely domesticated and live in hives provided by humans for the purpose of production of honey, however, they will leave these hives and form “wild” colonies in hollow trees, but there are no wild, native bees known. The castes of bees are: drones (sexually active males), a single queen (the egg-laying female), and workers (sexless females). The worker honey bees visit flowers to obtain nectar and pollen as their food, and construct the waxy combs made from secretions of the wax glands. The worker bees tend the eggs and larvae as well as feed the queen and carry away the eggs produced by the queen.

Honey crop

It is the amount of honey produced per bee colony per season.

Hormone

A hormone is any member of a class of signaling molecules, produced by glands in multicellular organisms, that are transported by the circulatory system to target distant organs to regulate physiology and behavior.

Horsepower continuous duty rate

It is as the term implies, the horsepower which can be supplied continuously (24 hours per day) by an engine without overheating.

Humanitarian engineering

A new engineering branch focuses on programs that are affordable, sustainable, and based on local resources, and it involves the creation and application of the innovative methods, processes, systems, and infrastructures to improving the well-being of marginalized people and disadvantaged communities, usually in the developing world. The word of “humanitarian” has been defined as “concerned with or seeking to promote human welfare.”

Humanitarian technology

A new professional field focuses on programs that are affordable, sustainable, and based on local resources, and it involves mainly application of the already developed simple methods, processes, systems, and infrastructures to improving the well-being of marginalized people and disadvantaged communities, usually in the developing world. Examples of humanitarian technologies for developing communities include affordable: (a) Technologies for clean water and sanitation; (b) Nonpolluting lighting, heating, and cooking methods; (c) Off-grid electricity generation (e.g., solar or bicycle); (d) Agricultural technologies and methods (e.g., aquaponics or irrigation); (e) Healthcare technologies; (f) Shelters; and (g) international STEAM education of Science, Technology, Engineering, Arts and Mathematics.

Hurricane

A tropical storm with winds of 74 miles per hour or more. Hurricanes form in the southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and eastern Pacific Ocean.

Hydraulic dredging

It is a floating barge type machine known as a cutter suction dredge used to remove underwater materials and transfer those sediments mixed with water (referred to as a slurry) through a pressurized pipeline to a deposit location.

Hydraulic retention time (HRT)

The given time it takes wastewater, including any return flows, to pass through a certain area

Hydrocarbons

Substances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.

Hydrochlorofluorocarbons (HCFCs)

Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone-depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases.

Hydrofluorocarbons (HFCs)

Compounds containing only hydrogen, fluorine, and carbon atoms. They were introduced as alternatives to ozone-depleting substances in serving many industrial, commercial, and personal needs. HFCs are emitted as by-products of industrial processes and are also used in manufacturing. They do not significantly deplete the stratospheric ozone layer, but they are powerful greenhouse gases with global warming potentials ranging from 140 (HFC-152a) to 11,700 (HFC-23).

Hydrogen sulfide gas (H₂S)

A gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly dangerous because it dulls the sense of smell so that it is unnoticeable after a prolonged period of time and because the odor is not noticeable in high concentrations. The gas is colorless, explosive, flammable, and poisonous to the respiratory system.

Hydrologic cycle

The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes’ heat transport from the equatorial to polar regions.

Hydrology

It is a branch of science concerned with the properties of the Earth’s water, and especially its movement in relation to land.

Hydrosphere

The component of the climate system comprising liquid surface and subterranean water, such as: oceans, seas, rivers, fresh water lakes, underground water etc.

Hypochlorination

Application of sodium hypochlorite (liquid) for disinfection is also called hypochlorination. It achieves the same result as that of chlorination using chlorine gas. Its use is generally limited to smaller water or wastewater treatment facilities or where there are significant health and safety concerns regarding the handling and use of chlorine gas.

Ice core

A cylindrical section of ice removed from a glacier or an ice sheet in order to study climate patterns of the past. By performing chemical analyses on the air trapped in the ice, scientists can estimate the percentage of carbon dioxide and other trace gases in the atmosphere at a given time. Analysis of the ice itself can give some indication of historic temperatures.

Ignitability

Any substance that exhibits any of the following properties is considered a hazardous substance due to ignitability: (a) a liquid that has a flash point less than 60 ° C; (b) a nonliquid capable, under normal conditions, of spontaneous and sustained combustion; (c) an ignitable compressed gas under the US Department of Transportation (DOT) regulations; and (d) an oxidizer under DOT regulations.

Impeller, pump

It is a spinning component, the heart of the dredge pump, that transmits energy from the motor which drives the pump to the fluid being pumped by advancing the fluid externally from the center of rotation.

Incident Command System (ICS)

A standardized on-scene emergency management construct specifically designed to provide an integrated organizational structure that reflects the complexity and demands of single or multiple incidents, without being hindered by jurisdictional boundaries. The Incident Command System is the combination of facilities, equipment, personnel, procedures, and communications operating within a common organizational structure, designed to aid in the management of resources during incidents. ICS is used for all kinds of emergencies and is applicable to small as well as large and complex incidents. ICS is used by various jurisdictions and functional agencies, both public and private, to organize field-level incident management operations.

Incineration

It is dry combustion of sludge or solid wastes to produce an inert ash. This ash can then be beneficially used or disposed of in a sanitary landfill. The process must dry the sludge cake or small solid wastes, destroy the volatile content by burning, and finally produce a sterile ash. A variety of incinerator configurations exist. The most common include: (a) multiple hearth furnace incinerator; and (b) fluidized bed incinerator.

Incinerator, fluidized bed

In the fluidized bed system, dewatered sludge or small solid waste is fed into a bed of hot sand fluidized by circulating air. There is rapid drying and combustion of the sludge or solid waste. Ash is carried out of the incinerator by the combustion gases and is separated by a wet scrubber system or equivalent.

Incinerator, multiple hearth furnace

Sludge passes downward through a series of hearths. Dewatered sludge cake or small solid wastes are fed to the top hearths. In the upper hearths, the water content is vaporized and the sludge or solid wastes are dried. In the middle hearths, the sludge or solid wastes are ignited and burned. In the lower hearths, the slow-burning materials is continuously burned, and the ash undergoes cooling.

Independent physicochemical wastewater treatment system (IPCWWTS)

An Independent Physicochemical Wastewater Treatment System (IPCWWTS) utilizes physicochemical (PC) process technology other than biological process technology to obtain combined primary and secondary treatment efficiency for removals of mainly biochemical oxidation demand (BOD), chemical oxidation demand (COD), total suspended solids (TSS), and phosphate. Typically, an IPCWWTS uses combinations of preliminary treatment (flow equalization, bar screening, comminution, grit chamber, ammonia stripping), chemical precipitation/coagulation, primary clarification (primary sedimentation clarification or primary flotation clarification), secondary clarification (secondary sedimentation clarification, or secondary flotation clarification, without biological treatment), tertiary wastewater treatment (filtration, and/or granular activated carbon adsorption, ion exchange, PC oxidation, etc.), and disinfection. An innovative efficient primary flotation clarifier or a secondary flotation clarifier can be in any shape, circular or rectangular. In general this IPCWWTS requires much less land area than conventional biological secondary treatment systems. Phosphors removal is inherent in this physicochemical process system.

Indirect emissions

Indirect emissions from a building, home or business are those emissions of greenhouse gases that occur as a result of the generation of electricity used in that building. These emissions are called “indirect” because the actual emissions occur at the power plant which generates the electricity, not at the building using the electricity.

Industrial Ecology (IE)

Industry, according to the Oxford English dictionary, is “intelligent or clever working” as well as the particular branches of productive labor. Ecology is the branch of biology that deals with the mutual relations between organisms and their environment. Ecology implies more the webs of natural forces and organisms, their competition and cooperation, and how they live off one another. Industrial ecology (IE) is now a branch of systems science for sustainability, or a framework for designing and operating industrial systems as sustainable and interdependent with natural systems. It seeks to balance Industrial production and economic performance with an emerging understanding of local and global ecological constraints.

Industrial revolution

A period of rapid industrial growth with far-reaching social and economic consequences, beginning in England during the second half of the eighteenth century and spreading to Europe and later to other countries including the United States. The industrial revolution marks the beginning of a strong increase in combustion of fossil fuels and related emissions of carbon dioxide [8].

Industry

It is intelligent or clever working as well as the particular branches of productive labor.

Inflow

Water discharged into a sewer system and service connections from sources other than regular connections. This includes flow from yard drains, foundation drains and around manhole covers. Inflow differs from infiltration in that it is a direct discharge into the sewer rather than a leak in the sewer itself.

Influent

Wastewater or other liquid—raw (untreated) or partially treated—flowing into a reservoir, basin, treatment process, or treatment plant.

Infrared radiation

Infrared radiation consists of light whose wavelength is longer than the red color in the visible part of the spectrum, but shorter than microwave radiation. Infrared radiation can be perceived as heat. The Earth’s surface, the atmosphere, and clouds all emit infrared radiation, which is also known as terrestrial or long-wave radiation. In contrast, solar radiation is mainly short-wave radiation because of the temperature of the Sun.

Infrared sludge dryer

It is a sludge dewatering process using regular direct radiant energy from infrared heating elements. Dewatered sludge is transferred from the dewatering equipment to the dryer by a conveyor belt. The sludge then drops into the augers, where the auger blades agitate the sludge while infrared heating elements heat the sludge. This process then repeats once the sludge is dropped into the secondary drying zone.

Innovative biological wastewater treatment system

It normally includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary flotation clarification for removing mainly total suspended solids from preliminary effluent, (c) secondary biological treatment units (such as activated sludge aeration or equivalent plus secondary flotation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent discharge standards.

Innovative physicochemical flotation wastewater treatment system

It includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber, etc., for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary flotation clarification for removing mainly total suspended solids from preliminary effluent, (c) secondary physicochemical treatment units (such as chemical precipitation/coagulation or equivalent plus secondary flotation clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent discharge standards. In the nitrification and denitrification steps, only tertiary flotation clarification will be used for solid-water separation.

Innovative physicochemical flotation-membrane wastewater treatment system

It includes (a) preliminary treatment units (i.e., screen, comminutor, grit chamber etc. for removal of sand, gravel, cinders, coffee grounds, small stones, cigarette filter tips, logs, cans, and other large-sized unwanted materials from raw wastewater), (b) primary flotation clarification for removing mainly total suspended solids from preliminary effluent, (c) secondary physicochemical treatment units (such as chemical precipitation/coagulation or equivalent plus secondary membrane clarification) for removing dissolved organic/inorganic pollutants from primary effluent, and (d) tertiary treatment plant units (i.e., filtration, granular activated carbon adsorption, ion exchange, oxidation, nitrification, denitrification, and/or disinfection) for final polishing the secondary effluent in order to meet the effluent discharge standards. In the nitrification and denitrification steps, only tertiary membrane clarification will be used for solid-water separation.

Insecticide

It is a substance used for killing insects.

Intergovernmental Panel on climate Change (IPCC)

The IPCC was established jointly by the United Nations Environment Programme and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature related to all significant components of the issue of climate change. The IPCC draws upon hundreds of the world’s expert scientists as authors and thousands as expert reviewers. Leading experts on climate change and environmental, social, and economic sciences from some 60 nations have helped the IPCC to prepare periodic assessments of the scientific underpinnings for understanding global climate change and its consequences. With its capacity for reporting on climate change, its consequences, and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official advisory body to the world’s governments on the state of the science of the climate change issue.

Internet

The Internet (portmanteau of interconnected network) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to link devices worldwide. It is a network of networks that consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, telephony, and file sharing.

Inundation

The submergence of land by water, particularly in a coastal setting.

Ion

A charged atom, molecule, or radical that affects the transport of electricity through an electrolyte or gas. An atom or molecule that has lost or gained one or more electrons

KAMET

It is the abbreviation of Krofta Advanced Municipal Effluent Treatment (KAMET), and is a circular package plant consisting of both Supracell and Sandfloat with Supracell on the top. KAMET system can be used for either water treatment or wastewater treatment, but is advertised for wastewater treatment.

Kraus activated sludge process

When nitrogen deficiency occurs in biological wastewater treatment and exogenous supply of nitrogen is expensive, the Kraus process can be useful in that an internal or endogenous supply of nitrogen is used to maintain the growth of active biomass. The Kraus process has a regular aeration tank (conventional, step aeration or complete mix) plus an extra reaeration tank. The reaeration tank receives (a) return activated sludge from a secondary clarifier, (b) digester supernatant, (c) digested sludge, and (d) possible other nitrogen source, if needed, and aerates the mixture. When the reaeration tank effluent is introduced into the aeration tank with the wastewater influent, the nitrate released from the reaeration tank serves as the supplemental nitrogen source for synthesis.

Ladder, dredge

It is a ladder that extends from the front position of the cutter suction dredge (CSD)and is attached to the pontoon by a hinge coupling. It is lowered by the dredge operator via controls located inside the control cab. The cutter head attached at the end of ladder excavates the material being dredged.

Lagoon, aerated

An aerated lagoon is a holding basin (3–10 days DT; 6–20 ft. depth) in which air is mechanically introduced to speed up aerobic decomposition of organic pollutants in wastewater. It is essentially the same as the extended aeration activated sludge biological process, except that an earthen basin is used for the aerobic suspended-growth bioreactor. The downstream of an aerated lagoon can be a facultative stabilization pond (or facultative lagoon), a sedimentation clarifier, or a dissolved air flotation clarifier, each incorporating the recycle of biological solids (or biosolids). The oxygen required by the aerated lagoon process is supplied by surface or diffused aerators. As with other suspended-growth systems, the turbulence created is used to maintain the contents of the basin in suspension.

Lagoon, anaerobic

Anaerobic lagoons are capable of treating high strength wastewater. They are relatively deep (8–20 ft. depth; 20–50 days DT) ponds with steep sidewalls in which anaerobic conditions are maintained by keeping wastewater organic loading so high that complete deoxygenation is prevalent. Although some oxygenation is possible in a shallow surface zone, once grease form an impervious surface layer, complete anaerobic conditions develop. Waste treatment or stabilization results from thermophilic anaerobic digestion of organic wastes. The treatment process is analogous to that occurring in single stage untreated anaerobic digestion of sludge in which acid forming bacteria break down organics. The resultant acids are then converted to carbon dioxide methane, cells and other products. In a typical anaerobic lagoon, raw wastewater enters near the bottom of the pond (often at the center) and mixes with the active microbial mass in the sludge blanket which is usually about 6 ft. deep. The effluent discharge is located near one of the sides of the pond, submerged below the liquid surface. Excess undigested grease floats to the top, forming a heat retaining and relatively airtight cover. Wastewater flow equalization and heating are generally not practiced. Excess sludge is washed out with the lagoon effluent. Recirculation of waste sludge is not required.

Lagoon, facultative

Facultative lagoons are intermediate depth (3–8 ft. depth; 20–180 days DT) ponds in which the wastewater is stratified into three zones. These zones consist of an anaerobic bottom layer, an aerobic surface layer, and an intermediate zone. Stratification is a result of solids settling and temperature-water density variations. Oxygen in the surface stabilization zone is provided by reaeration and photosynthesis. This is in contrast to aerated lagoons in which mechanical aeration is used to create aerobic surface conditions. In general the aerobic surface layer serves to reduce odors while providing treatment of soluble organic by-products of the anaerobic processes operating at the bottom. Sludge at the bottom of facultative lagoons will undergo anaerobic digestion producing carbon dioxide, methane, and cells. The photosynthetic activity at the lagoon surface produces oxygen diurnally, increasing the dissolved oxygen during daylight hours, while surface oxygen is depleted at night. It is used for treating raw, screened wastewater, or primary effluent, secondary effluent, or weak biodegradable industrial wastewater.

Lake dredging

Lake dredging helps to maintain a healthy environment for both aquatic life and recreational activities because both natural and man-made lakes eroding sediment, silt accumulation, and algae blooms can gradually build up causing both depth and water quality issues.

Lake

An inland body of water, fresh or salt, of considerable size usually greater than 50 acres (200,000 square meters) and occupying a basin or hollow on the Earth’s surface.

Land reclamation

It is a process consisting of dredging sand, clay, or rock from offshore or inland lakes, ponds, and quarries. The dredged material is repurposed as fill material forming new land along coastal waterways or inland water bodies, such as swamps.

Landfill

Land waste disposal site in which waste is generally spread in thin layers, compacted, and covered with a fresh layer of soil each day.

Landfill, sanitary

Burying sludge or solid wastes to minimize nuisance conditions or public health problem is called sanitary landfill. Sludge and solid wastes are buried in layers which are covered with fill material excavated at the site. Landfills must be located where nearby wells and groundwater supplies will not be contaminated by leachate from the landfill operation. Sludge landfills are generally separate from refuse landfills.

Landslide

Processes that result in the downward movement of falling or flowing rock, soil, organic materials, or a combination of these.

Latitude

The location north or south in reference to the equator, which is designated at zero (0) degrees. Lines of latitude are parallel to the equator and circle the globe. The North and South poles are at 90° North and South latitude.

Latrine

It is a receptacle (like a toilet or something as simple as a pit in the ground) for use as a sanitation system which functions to receive human excreta.

Laundromat

An establishment with coin-operated washing machines and dryers for public use.

Layer, data

It is a logical set of thematic data described and stored in a map library. Layers act as digital transparencies that can be laid atop one another for viewing or spatial analysis.

Leaf-cutting bee (Megachile pascoensis)

They prepare a tunnel in the ground or in rotten wood. The female flies to a suitable flower and cuts parts out of the petals, or the leaves. These round disks are brought back to the tunnel and used construct a small cradle. The female also collect foods for other bees. They are natural bees of wild species, not affecting humans.

Least developed country

A country with low indicators of socioeconomic development and human resources, as well as economic vulnerability, as determined by the United Nations.

Line data

Lines represent geographic features too narrow to be displayed as an area at a given scale, such as contours, street centerlines, or streams.

Listed wastes

In the USA, the government listed wastes are wastes specifically regulated by the US Environmental Protection Agency (USEPA) and appear on one of four lists found in 40CFR 261.3. The four USEPA lists, however, fall into three categories of wastes: (a) nonspecific source wastes, such as generic wastes, commonly produced wastes by CFR 261.32; (c) commercial chemical products, such as wastes including specific commercial chemical products or manufacturing chemical intermediates—creosote and kepone, etc., under 40 CFR 261.33 (e) and (f).

Long-wave radiation

Radiation emitted in the spectral wavelength greater than about 4 micrometers, corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as “terrestrial radiation” or “infrared radiation,” although somewhat imprecisely.

Make-up water

Water that is added to the tower to replenish water losses due to evaporation, drift, blow-down, and other miscellaneous water losses.

Marina dredging

It is an operation for maintaining the depth of a marina, whether private or public, is vital to both marina owners and the customers they serve. Adequate channel depths allow boaters to safely move in and out while protecting vessels from damage.

Masking agents

Substances used to cover up or disguise unpleasant odors. Liquid masking agents are dripped into the wastewater, sprayed into the air, or evaporated (using heat) with the unpleasant fumes or odors and then discharged into the air by blowers to make an undesirable odor less noticeable.

Mason bee (Osmia cobaltina)

This bee nests in the ground or in natural cavities in wood. Mason bees lack the pollen baskets on their tibiae. They carry their pollen in a “pollen brush” on the underside of the abdomen. They are natural bees of wild species, not affecting humans.

Mathematical modeling

The process of developing a mathematical model is termed mathematical modeling.

Mathematical models

A mathematical model is a description of a system using mathematical concepts and language. A model may help to explain a system and to study the effects of different components, and to make predictions about costs, impact, population, behavior, frequency, etc.

Mechanical aeration

The use of machinery to mix air and water so that oxygen can be absorbed into the water.

Mechanical dredging

It is an operation for removing debris or compressed hardened elements from below the water using a clamshell type bucket or heavy-duty excavator. This method is preferred when both dredging and placing elements nearby onshore or onto a barge for further transport to a designated disposal location.

Megacities

Cities with populations over ten million.

Melliferous

It is a situation of yielding or having to do with honey.

Membrane bioreactor (MBR)

Currently it is one of suspended growth biological processes (such as activated sludge process) involving the use of a bioreactor (such as an aeration tank) for carbonaceous oxidation, nitrification and/or denitrification, and the use of membrane filtration for subsequent bioreactor effluent treatment. The membrane filter discharges the membrane filter effluent (as the product water), recycles certain amount of activated sludge to the bioreactor, and wastes the excess amount of activated sludge. It the future, an MBR may also be a combination of an attached growth bioreactor and a membrane filter.

Metadata

It is the information about a data set. It may include the source of the data; its creation date and format; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard.

Metazoan

It is a group of small animals that may be present in wastewater having bodies composed of cells that are differentiated into tissues and organs, such as rotifers, water bears, and daphnia.

Methane (CH₄)

A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 25 times that of carbon dioxide (CO₂). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The GWP is from the IPCC’s Fourth Assessment Report (AR4).

Metric ton

Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 lbs. or 1.1 short tons.

Microorganisms

Very small organisms that can be seen only through a microscope. Some microorganisms use the wastes in wastewater for food and thus remove or alter much of the undesired matter.

Miticide

It is a substance that kill mites.

Mitigation

(a) A human intervention to reduce the human impact on the climate system; it includes strategies to reduce greenhouse gas sources and emissions and enhancing greenhouse gas sinks; (b) Activities taken to reduce the loss of life and lessen the impact to property from disasters.

Mixed liquor suspended solids (MLSSs)

(a) The concentration of suspended solids present in activated sludge mixed liquor, usually expressed as milligrams per liter (mg/L); (b) Suspended solids in the mixed liquor of an aeration tank.

Mixed liquor volatile suspended solids (MLVSS)

(a) The fraction of the suspended solids in biological reactor’s mixed liquor that can be burned off by combustion at 550 ° C., or the organic portion of the solids (an estimation of the microorganisms and food). Usually expressed as milligrams per liter (mg/L). (b) The organic or volatile suspended solids in the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of the microorganisms present.

Mixed liquor (ML)

(a) The water containing biosolids in a biological reactor. (b) When the activated sludge in an aeration tank is mixed with primary effluent or the raw wastewater and return sludge, this mixture is then referred to as mixed liquor as long as it is in the aeration tank. Mixed liquor may also refer to the contents of mixed aerobic or anaerobic digesters.

Mixed wastes

The entire volume of any waste mixture containing a listed hazardous waste, regardless of concentration, is considered a hazardous waste with the following exceptions: (a) the listed waste in the mixture was listed solely because it exhibits a hazardous waste characteristic and the mixture no longer exhibits that characteristic; (b) a wastewater discharge subject to regulation by the Clean Water Act (CWA) and the hazardous waste mixed with the mixtures of nonhazardous wastes and characteristic hazardous wastes if the mixture no longer exhibits any of the characteristics (ignitability, corrosivity, reactivity, and toxicity); (c) a wastewater discharge subject to regulation by the Clean Water Act (CWA) and the hazardous waste mixed with the waste water which concentration of carcinogenic and non-carcinogenic spent solvents listed in 40 CFR Part 261.31 in the wastewater, provided the concentration does not exceed 1 ppm and 25 ppm, respectively; (d) a wastewater discharge subject to regulation by the Clean Water Act (CWA) and the hazardous waste mixed with the small loss of discarded commercial chemical products or intermediaries used as raw materials in manufacturing or produced as by-products; (e) a wastewater discharge subject to regulation by the Clean Water Act (CWA) and the hazardous waste mixed with a laboratory wastewater containing small amounts of listed toxic wastes; (f) a wastewater discharge subject to regulation by the Clean Water Act (CWA) and the hazardous waste mixed with the heat exchanger bundle cleaning sludge (petroleum refining industry).

Multiple hearth furnace incinerator

Sludge passes downward through a series of hearths. Dewatered sludge cake or small solid wastes are fed to the top hearths. In the upper hearths, the water content is vaporized and the sludge or solid wastes are dried. In the middle hearths, the sludge or solid wastes are ignited and burned. In the lower hearths, the slow-burning materials is continuously burned, and the ash undergoes cooling.

Municipal solid waste (MSW)

Residential solid waste and some non-hazardous commercial, institutional, and industrial wastes. This material is generally sent to municipal landfills for disposal.

Natural gas

Underground deposits of gases consisting of 50 to 90 percent methane (CH₄) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C₃H₈) and butane (C₄H₁₀).

Natural resources

These resources naturally exist, such as surface water, groundwater, ice, snow, air, plants, animals, minerals, metals, soils, rocks, oils, underground gases, light, winds, radiation, etc. that are useful or potentially useful. Uses of natural resources include agricultural, industrial, household, recreational and environmental activities.

Natural variability

Variations in the mean state and other statistics (such as standard deviations or statistics of extremes) of the climate on all time and space scales beyond that of individual weather events. Natural variations in climate over time are caused by internal processes of the climate system as well as changes in external influences, such as volcanic activity and variations in the output of the sun.

Nectar flow

(a) It is a time of harvest when nectar is plentiful and bees produce and store surplus honey; also called honey flow. (b) It is called honey flow which is a time when nectar is plentiful and bees produce and store surplus honey.

NGO

It is a Nongovernmental Organization. Any nonprofit, voluntary citizens’ organization which can be organized at a local, national or international level.

Nitrate (NO₃)

An oxygenated form of nitrogen.

Nitrification

It is a biological process by which ammonia in wastewater is converted by Nitrosomonas and Nitrobacter to nitrite, then to nitrate in the presence of oxygen. The biological reactions involved in these conversions may take place during activated sludge treatment, or a separate stage following removal of carbonaceous materials. Separate stage nitrification may be accomplished via suspended growth or attached growth unit processes. In either case, the nitrification step is preceded by a pretreatment sequence (i.e., preliminary treatment, primary treatment, and secondary treatment). Possible secondary treatment may be (a) biological secondary treatment, such as activated sludge, trickling filter, roughing filter, plus secondary clarification; or (b) physicochemical secondary treatment, such as chemical precipitation/coagulation plus secondary clarification. Low BOD (i.e., BOD₅/TKN ratio of less than 3) in the secondary effluent will assure a high concentration of nitrifiers (Nitrosomonas and Nitrobacter) in the nitrification biomass. The most common separate stage nitrification process is the plug flow suspended growth configuration with clarification. In this process, pretreatment effluent (i.e., nitrification influent) is pH adjusted as required, and aerated, in a plug flow mode. Because the carbonaceous demand is low, nitrifiers predominate. A clarifier (either sedimentation clarifier or flotation clarifier) follows aeration, and nitrification sludge is returned to the aeration tank. A possible modification is the use of pure oxygen in place of conventional aeration during the plug flow operation.

Nitrifier (nitrifying bacteria)

Bacteria that are capable of oxidizing nitrogenous material, such as Nitrobacter and Nitrosomonas .

Nitrifying bacteria

Bacteria that change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate).

Nitrite (NO₂)

It is an intermediate oxygenated form of nitrogen

Nitrite Lock

Incomplete nitrification resulting in excess nitrite levels that react with chlorine. Also known as “chlorine sponge.”

Nitrobacter

It is a group of nitrifying bacteria that oxidize nitrite to nitrate.

Nitrogen (N)

N is an essential nutrient that is often present in wastewater as ammonia, nitrite, nitrate, and organic nitrogen. The sum of these is expressed as total nitrogen.

Nitrogen cycle

(a) It is a chemical transformation cycle of nitrogen through various stages of decomposition and assimilation. (b) The natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle, including nitrous oxide (N₂O) and nitrogen oxides (NOx).

Nitrogen gas (N₂)

Gaseous form of nitrogen, N, also called atmospheric nitrogen. It comprises approximately 79% of atmospheric gas.

Nitrogen oxides (NOx)

Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced in the emissions of vehicle exhausts and from power stations. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), can impair visibility, and have health consequences; they are thus considered pollutants.

Nitrogenous biochemical oxygen demand (NBOD)

The quantitative measure of the amount of oxygen required for the biological oxidation of nitrogenous material, such as ammonia-nitrogen and organic nitrogen (Measured by subtracting carbonaceous BOD from total BOD values).

Nitrosomonas

A genus of nitrifying bacteria that oxidize ammonia to nitrite.

Nitrous oxide (N₂O)

A powerful greenhouse gas with a global warming potential of 298 times that of carbon dioxide (CO₂). Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning. The GWP is from the IPCC’s Fourth Assessment Report (AR4). Natural emissions of N₂O are mainly from bacteria breaking down nitrogen in soils and the oceans. Nitrous oxide is mainly removed from the atmosphere through destruction in the stratosphere by ultraviolet radiation and associated chemical reactions, but it can also be consumed by certain types of bacteria in soils.

NOAA Weather Radio

A radio with a special receiver to receive information from the network of radio stations that broadcast continuous weather information from the National Weather Service.

Nocardia

It is a group of irregularly bent, short branching filamentous organisms that cause dense dark foam in aeration basins. Associated with high fats, oils, and greases. Easily identified under a microscope.

Nonionic polymer

A neutrally charged colloidal big organic substance used as a coagulant to aid in separating (settling or floating) solids in water or wastewater

Nonmethane volatile organic compounds (NMVOCs)

Organic compounds, other than methane, that participate in atmospheric photochemical reactions.

Nonstructural elements

Any portion of the building or grounds not connected to the main structure (e.g., bookshelves, file cabinets, furnishings).

NPDES permit

National Pollutant Discharge Elimination System (NPDES) permit is the US regulatory agency document issued by either a federal or state agency which is designed to control all discharges of pollutants from all point sources and storm water runoff into US waterways. A treatment plant that discharges to a surface water will have a NPDES permit.

Nutrient ratio

The ratio of carbon, nitrogen, phosphorus and sometimes other trace elements that is essential to optimum growth of the biomass in activated sludge.

Nutrient

A substance that is taken in by organisms and promotes growth. Carbon, nitrogen, and phosphorus are essential nutrients to most aquatic organisms.

Ocean acidification

Increased concentrations of carbon dioxide in sea water causing a measurable increase in acidity (i.e., a reduction in ocean pH). This may lead to reduced calcification rates of calcifying organisms such as corals, mollusks, algae and crustaceans.

Organic

A volatile, combustible, or biodegradable compound containing carbon bound with other elements.

Organic nitrogen

It is an organic nutrient containing nitrogen which is chemically bound in organic molecules such as proteins, amines, and amino acids. It is calculated by subtracting the Ammonia Nitrogen analysis results from Total Kjeldahl Nitrogen analysis results.

Organic phosphate

(a) It is a molecule of phosphate combined with an organic compound. Total phosphorus includes orthophosphate, polyphosphate and organic phosphate. (b) It is an organic phosphorus originating from organic sources, such as body and food waste, and sometimes industrial sources. Some can biologically decompose into inorganic orthophosphate; other types are non-biodegradable and will pass through the wastewater system without treatment.

Organic solvent

A carbon-based solvent that is capable of dissolving other substances.

Ortho Imagery

It is the aerial photograph that has been rectified to produce an accurate image of the Earth by removing tilt and relief displacements, which occurred when the photo was taken.

Orthophosphate

It is an inorganic nutrient containing phosphorus which is required for plant and animal growth. An inorganic, soluble form of phosphorus that is readily available to plants and animals without further breakdown, and accounts for 70–90% of total phosphorus in wastewater. The easiest form of phosphorus that can be treated chemically. Total phosphorus includes orthophosphate, polyphosphate and organic phosphate.

OSHA

It stands for the Occupational Safety and Health Administration of the United States Department of Labor, formed by the Occupational Safety and Health Act of 1970.

Output rating

It refers to the percent of solid material production which may be expected from the dredge under normal operating conditions. Not to be confused with such phrases as output capacity, which usually refers to theoretical pumping output which could be more than twice as much under certain conditions.

Oxic

It is an environmental condition in which an aquatic environment contains limited dissolved oxygen only in the range of 1.5 to 2.0 mg/L.

Oxidation ditch

It is a ring-shaped channel suspended-growth biological process system similar to extended aeration process for mainly carbonaceous oxidation and nitrification. It was developed to minimize waste-activated sludge production through endogenous decay of the sludge mass. It is equipped with mechanical aeration devices, such as, mechanical brush aerators surface aerators and jet aerator devices to aerate and pump the wastewater. Screened wastewater enters the ditch is aerated, and circulates at about 0.8 to 1.2 ft./sec. The economics of oxidation ditches appear most favorable when the solids retention time (SRT) is long, particularly where nitrification is required. When both nitrification and denitrification are required, certain portion of the ditch must be operated under anoxic condition (instead of normal aerobic oxidation condition), the process should be renamed as “oxidation-denitrification ditch.”

Oxidation reduction potential (ORP)

The potential required to transfer electrons from the oxidant to the reductant; the quantitative measure, in mV, of the state of oxidation in wastewater treatment.

Oxidation

The addition of oxygen, removal of hydrogen, or removal of electrons from a compound (For instance, organic matter may be oxidized to a more stable compound).

Oxidize

To chemically transform a substance by combining it with oxygen.

Ozonation

It is an oxidation process or a disinfection process, or both, involving the use of ozone.

Ozone (O₃)

Ozone is a toxic and corrosive oxidant, or disinfectant. Ozone gas cannot be stored and must be produced on site. Ozone is produced by passing air or oxygen between oppositely charged plates or through tubes in which a core and the tube walls serve as the oppositely charged surfaces. Ozone is an excellent disinfectant or oxidant, but is harmful lung irritant. Therefore, un-reacted ozone must be vented through a destruction unit (usually thermal destruction).

Ozone-depleting substance (ODSs)

A family of man-made compounds that includes, but are not limited to, chlorofluorocarbons (CFCs), bromofluorocarbons (halons), methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds have been shown to deplete stratospheric ozone, and therefore are typically referred to as ODSs.

Ozone layer

The layer of ozone that begins approximately 15 km above Earth and thins to an almost negligible amount at about 50 km, shields the Earth from harmful ultraviolet radiation from the sun. The highest natural concentration of ozone (approximately 10 parts per million by volume) occurs in the stratosphere at approximately 25 km above Earth. The stratospheric ozone concentration changes throughout the year as stratospheric circulation changes with the seasons. Natural events such as volcanoes and solar flares can produce changes in ozone concentration, but man-made changes are of the greatest concern.

Ozone precursors

Chemical compounds, such as carbon monoxide, methane, nonmethane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere.

Ozone

Ozone, the triatomic form of oxygen (O₃), is a gaseous atmospheric constituent. In the troposphere, it is created by photochemical reactions involving gases resulting both from natural sources and from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide range of living organisms. Tropospheric ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O₂). Stratospheric ozone plays a decisive role in the stratospheric radiative balance. Depletion of stratospheric ozone, due to chemical reactions that may be enhanced by climate change, results in an increased ground-level flux of ultraviolet (UV) B radiation.

Package treatment plant

A prefabricated water or wastewater treatment plant consisting of two or more unit processes.

Packing

Also called fill, this is a product placed within the tower to promote uniform water flow distribution and to enhance water-air contacts. (Note: Again, note the similarity to wet scrubbing applications.)

Parasite

It is an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host’s expense.

Particulate matter (PM)

Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists, or aerosols. The physical characteristics of particles, and how they combine with other particles, are part of the feedback mechanisms of the atmosphere.

Particulate

Solids suspended in water, wastewater, or air that can vary widely in shape, size, density, and charge.

Parts per billion (ppb)

Number of parts of a chemical found in one billion parts of a particular gas, liquid, or solid mixture.

Parts per million by volume (ppmv)

Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid.

Parts per trillion (ppt)

Number of parts of a chemical found in one trillion parts of a particular gas, liquid, or solid.

Pathogen

It is a bacterium, virus, or other microorganism that can cause disease.

Pathogenic organisms

Bacteria, viruses, or cysts, which can cause disease (typhoid, cholera, dysentery) in a host such as a human. Also called pathogens.

Percolation

The movement or flow of water through soil or rocks.

Perennial crops

They are crops developed to reduce inputs necessary to produce food by greatly reducing the need to replant crops from year to year.

Perfluorocarbons (PFCs)

A group of chemicals composed of carbon and fluorine only. These chemicals (predominantly CF4 and C2F6) were introduced as alternatives, along with hydrofluorocarbons, to the ozone-depleting substances. In addition, PFCs are emitted as by-products of industrial processes and are also used in manufacturing. PFCs do not harm the stratospheric ozone layer, but they are powerful greenhouse gases: CF4 has a global warming potential (GWP) of 7390 and C2F6 has a GWP of 12,200. The GWP is from the IPCC’s Fourth Assessment Report (AR4). These chemicals are predominantly human-made, though there is a small natural source of CF4.

Performance

Normally expressed as the amount of cooling for a given quantity of water at a given wet bulb temperature.

Permafrost

Perennially (continually) frozen ground that occurs where the temperature remains below 0 ° C for several years.

Pest

A destructive insect or other animal that attacks crops, food, livestock, human, or structure, etc. For instance, the tomato plant attracts a pest called whitefly, and the wood frame house attracts a pest called termite.

Pesticide

It is a substance, usually a chemical, used for destroying insects or other organisms harmful to cultivated plants or to animals

pH

(a) The negative logarithm of the hydrogen ion concentration (−log10[H⁺]) where H⁺ is the hydrogen-ion concentration in moles per liter. Neutral water has a pH value of 7. (b) An expression of both acidity and alkalinity on a scale of 0 to 14, with 7 representing neutrality; numbers less than 7 indicate increasing acidity and numbers greater than 7 indicate increasing alkalinity. Acid rain can increase the pH level of the water in a lake, thereby killing all life.

pH adjustment

A means of maintaining the optimum pH through the use of chemical additives.

Phenology

The timing of natural events, such as flower blooms and animal migration, which is influenced by changes in climate. Phenology is the study of such important seasonal events. Phenological events are influenced by a combination of climate factors, including light, temperature, rainfall, and humidity.

Pheromones

They are chemical substances secreted from bee glands and used as a means of communication; honey bees secrete many different pheromones.

Phosphate

PO₄³⁻ ion

Phosphorus (P)

P is an essential element and nutrient for all life forms. Occurs as orthophosphate, polyphosphate, and organic phosphates, the sum of which is total phosphorus.

Phosphorus-accumulating organisms (PAOs)

Microorganisms (bacteria) that are capable of uptaking and storing orthophosphate in excess of their biological requirements.

Photosynthesis

(a) The process by which plants take CO₂ from the air (or bicarbonate in water) to build carbohydrates, releasing O₂ in the process. There are several pathways of photosynthesis with different responses to atmospheric CO₂ concentrations. (b) The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll, using sunlight as an energy source. Plants thereby absorb carbon from the atmosphere with the process, and store it in their forms.

Physical recovery

Identification of possible relocation areas for operations as well as plans to restore services, equipment, materials, and buildings and grounds after an incident.

Phytoplankton

Usually microscopic aquatic plants, sometimes consisting of only one cell.

Pit latrine (Also Simple pit latrine)

It is the cheapest and most basic form of improved sanitation, which consists of a pit dug into the ground with some kind of sturdy cover with a hole in it through which excreta goes into the pit.

Plankton

Those organisms that are unable to maintain their position or distribution independent of the movement of water or air masses.

Plugging

It is a term used to indicate when the material within a slurry that is being hydrotransported slows down, then settles, and plugs or clogs the discharge pipeline.

Point, data

It is a single x,y coordinate that represents a geographic feature too small to be displayed as a line or area at that scale.

Pollination

It is a process involving the transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower; pollination is a prerequisite for fertilization, and fertilization allows the flower to develop seeds.

Pollinator

It is the biotic agent (vector) that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or “syngamy” of the female gametes in the ovule of the flower by the male gametes from the pollen grain.

Pollution

The contamination of a natural ecosystem, especially with reference to the activity of humans.

Pollution control

A wide range of techniques, solutions, practices, and services for treating wastewater and waste.

Polygon

It is a multisided figure that represents area on a map. Polygons have attributes that describe the geographic feature they represent.

Polyhydroxyalkanoates (PHAs)

Energy-rich carbon polymers inside a bacterial cell, which are converted from readily available organic molecules, such as volatile fatty acids (VFAs), in the wastewater. PHAs are the intracellular energy storage of the phosphorus-accumulating organisms (PAOs). The PAOs utilize PHA as an energy source to uptake phosphorus from the wastewater in the aerobic zone of the biological phosphorus removal process.

Polymer

Used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water.

Polyphosphate (Poly-P)

(a) Inorganic phosphorus derived from synthetic detergents. May be hydrolyzed into orthophosphates. (b) It is a large molecule containing many individual molecules of orthophosphate. Total phosphorus includes orthophosphate, polyphosphate, and organic phosphate.

Ponding

A condition occurring on trickling filters when the hollow spaces (voids) become plugged to the extent that water passage through the filter is inadequate. Ponding may be the result of excessive slime growths, trash, or media breakdown.

Postaeration

It is one of the tertiary treatment processes. Because of the more stringent water quality standards being adopted by various regulatory agencies, the practice of postaeration has increased substantially in recent years. The introduction of water-quality-based effluent standards and permits that include high dissolved oxygen levels has made it necessary for many wastewater treatment plants to postaerate the plant effluent before discharge.

Pour-flush latrine

It is a latrine where a small quantity of water is poured in to flush excreta through a water seal into a pit.

Powdered activated carbon adsorption

Powdered activated carbon (PAC) is used in both water and wastewater treatment. For water treatment, PAC systems generally involve dosing powdered activated carbons in slurry form to rapid mixers and flocculators (for mixing and flocculation, and adsorption) before reaching clarifiers for PAC-floc separation and clarifier effluent discharge. For wastewater treatment, powdered activated carbon in slurry form is dosed to either mixing/flocculation chambers (if they exist), or to an aeration basin directly to be mixed with mixed liquor for adsorption reactions. The spent PAC again is recovered or removed by a subsequent clarifier (either sedimentation clarifier or flotation clarifier). When PAC is used in conjunction with a flotation clarifier, it is also called “adsorption flotation.”

Preaeration

Preaeration is one of the preliminary treatment processes. It promotes a more uniform distribution of suspended and floating solids. Aerating wastewater prior to primary clarification (sedimentation or flotation) can also improve its treatability, provide grease separation, odor control, grit removal and flocculation, and increase BOD removals. It is now common to combine grit removal with preaeration as one unit process. Since dissolved air flotation (DAF) will provide aeration for grease separation, odor control, and oxidation, preaeration is not needed if DAF is used for primary flotation clarification (instead of sedimentation clarification).

Precession

The wobble over thousands of years of the tilt of the Earth’s axis with respect to the plane of the solar system.

Precipitate

An insoluble, finely divided substance, which is a product of a chemical reaction, or a natural hydrological reaction.

Precipitation

Any and all forms of water, whether liquid or solid, that fall from the atmosphere and reach the Earth’s surface. A day with measurable precipitation is a day when the water equivalent of the precipitation is equal to or greater than 0.2 mm.

Precision

The degree to which a set of observations or measurements of the same property, usually obtained under similar conditions, conform to themselves; a data quality indicator. Precision is usually expressed as standard deviation, variance, or range, in either absolute or relative terms.

Preliminary effluent

The effluent from a preliminary treatment system (i.e., bar screen, comminutor, and grit chamber) by which most of large objects, such as rocks, logs and cans, grit, etc., in raw wastewater have been removed.

Preliminary treatment

It is the first treatment step, or preliminary step, of either a conventional wastewater treatment system or an independent physicochemical treatment system. Preliminary treatment consists of bar screen, comminutor, and grit chamber mainly for removing large objects, such as rocks, logs and cans, grit, etc., from raw wastewater. Comminutor is an option depending on the nature and characteristics of raw wastewater.

Prevention

Actions taken to avoid an incident or to intervene to stop an incident from occurring.

Primary effluent

The effluent from a primary treatment system (either primary sedimentation clarification or primary flotation clarification) by which most of total suspended solids in wastewater have been removed.

Primary flotation clarification

A dissolved air flotation clarification process, which is used for primary clarification of wastewater with a main purpose of total suspended solids removal.

Primary flotation clarification

It is a unit process or unit operation for removal of mainly total suspended solids (settleable solids and floatable solids) from screened wastewater using a primary flotation clarifier.

Primary flotation clarifier

A dissolved air flotation (DAF) reactor is used to float total suspended solids (TSSs) from screened wastewater by decreasing their apparent density. DAF consists of saturating a portion or all of the wastewater feed, or a portion of recycled effluent with air at a pressure of 25 to 90 lb./square inch (gage). The pressurized wastewater is held at this pressure for 0.5 to 3 minutes in a retention tank and then released to atmospheric pressure to the flotation chamber. The sudden reduction in pressure results in the release of microscopic air bubbles, which attach themselves to TSS and oil particles in the wastewater in the flotation chamber. This results in agglomeration, which, due to the entrained air, have greatly increased vertical rise rates of about 0.5 to 2 ft./min. The floated materials rise to the surface to form a froth layer (float). Specially designed scrapers or other skimming devices continuously remove the froth (or float). The retention time in the flotation chambers is usually about 20–60 minutes for rectangular flotation clarifier, and about 3–15 minutes for circular flotation clarifier using zero-horizontal velocity design. The effectiveness of dissolved air flotation depends upon the attachment of bubbles to the suspended solids and/or oil, which are to be removed from the waste stream. The attraction between the air bubble and particle is primarily a result of the particle surface charge and bubble-size distribution. The more uniform the distribution of water and microbubbles, the shallower the flotation clarifier can be. Generally, the depth of effective flotation units is between 3 and 9 feet.

Primary sedimentation clarification

It is a unit process or unit operation for removal of mainly total suspended solids (settleable solids and floatable solids) from screened wastewater using a primary sedimentation clarifier.

Primary sedimentation clarifier

It is a tank used to settle mainly total suspended solids (TSSs) from screened raw wastewater by gravity. The main objectives of a primary sedimentation clarifier are removal of settleable solids by settling them to the clarifier bottom, and removal of floatable solids by skimming them from the clarifier’s wastewater surface. In a rectangular sedimentation clarifier, the wastewater flows from one end to the other and the settled sludge is moved to a hopper at on end, either by scrapers called “flights” set on parallel chains, or by a single bottom scraper set on a traveling bridge. Floating materials, such as grease and oil, are collected by a surface skimmer and then removed from the rectangular sedimentation clarifier. In a circular sedimentation clarifier, the wastewater usually enters in the middle and flows toward the outside edge. Settled sludge is pushed to the hopper that is in the middle of the circular clarifier’s tank bottom. Floating material is removed by a surface skimmer connected to the sludge collector.

Primary swarm

It is the first swarm to leave the parent colony, usually with the old queen (see secondary swarm).

Primary treatment

It is an important wastewater treatment step (either primary sedimentation clarification or primary flotation clarification mainly for removing total suspended solids from preliminary treatment effluent) after the preliminary treatment (i.e., bar screen, comminutor, and grit chamber mainly for removing large objects from raw wastewater), but before secondary treatment (either biological treatment or physicochemical treatment mainly for removing dissolved organic/inorganic pollutants from primary effluent).

Procedure

A set of systematic instructions for performing an operation.

Propolis

(a) It is called bee glue, which is sap or resinous material that is collected from trees or plants by bees and used to strengthen the comb and to seal cracks. (b) They are sap or resinous materials collected from trees or plants by bees and used to strengthen the comb and to seal cracks; also called bee glue

Protozoan

Small, one-celled animals such as amoebae, ciliates, and flagellates.

Queen bee

It is a female bee with a fully developed reproductive organ, and larger and longer than a worker bee. The queen is the center of the hive. She produces all of the eggs, the majority of which develop into worker bees, some into male drones, and a few occasionally become young queens, only when necessary.

Radiation

Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object.

Radiative forcing

A measure of the influence of a particular factor (e.g., greenhouse gas (GHG), aerosol, or land use change) on the net change in the Earth’s energy balance.

Ramming

It is a term applied to the excessive shock to which the dredge pump is subjected to as a result of suddenly losing and regaining suction.

Rapid mixing

A water treatment unit process of quickly mixing a chemical solution uniformly through the process water.

Raw wastewater

Plant influent or wastewater BEFORE any treatment.

Reactivity

Any substance exhibits the characteristic of reactivity if it has any of the following properties: (a) it is normally unstable and readily undergoes violent change without detonation; (b) it reacts violently with water; (c) it forms potentially explosive mixtures with water; (d) when mixed with water, it generates toxic gases, vapors, or fumes in a quantity sufficient to present a danger to human health or the environment; (e) it is a cyanide- or sulfide-bearing substance, which, when exposed to pH conditions between 2 and 12.5, can generate toxic gases, vapors, or fumes in a quantity sufficient to present a danger to human health or the environment; (f) it is capable of detonation or explosive reaction if subjected to a strong initiating source or if heated under confinement; (g) it is readily capable of detonation or explosive decomposition or reaction at standard temperature and pressure; (h) it is forbidden explosive as defined in 49 CFR 173.51, or a Class A explosive as defined in 49 CFR 173.53 or Class B explosive as defined in 49 CFR 173.88.

Reagent

A chemical substance used to cause a reaction for the purpose of chemical analysis.

Reagent blank

A sample consisting of reagent(s), without the target analyte or sample matrix, introduced into the analytical procedure at the appropriate point and carried through all subsequent steps to determine the contribution of the reagents and of the involved analytical steps to error in the observed value.

Reagent grade

The second highest purity designation for reagents, which conform to the current specifications of the American Chemical Society Committee on Analytical Reagents.

Reagent solution

A distilled water containing a chemical substance used to cause a reaction for the purpose of chemical analysis.

Receiving water

A stream, river, lake, ocean, or other surface or groundwater into which treated or untreated wastewater is discharged.

Recirculation

The return of part of the effluent from a treatment process to the incoming flow.

Recovery plant

(a) It is a plant designed to recover minerals such as ore. Dredges can pump a slurry via the discharge pipeline directly to a recovery plant where water and material are separated. (b) It is a plant designed to recover wastewater for water reuse.

Recycling

Collecting and reprocessing a resource so that it can be used again. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products.

Reduction

A chemical reaction involving the addition of electrons to a chemical entity.

Refinery

A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value.

Refining waste

A refining waste or refinery waste is the waste or wastewater from a refinery.

Reflectivity

The ability of a surface material to reflect sunlight including the visible, infrared, and ultraviolet wavelengths.

Reforestation

Planting of forests on lands that have previously contained forests but that have been converted to some other use.

Relative humidity

The ratio of the partial pressure of water vapor in the air to the vapor pressure of water at the temperature of the air, which contains the water vapor.

Relative sea level rise

The increase in ocean water levels at a specific location, taking into account both global sea level rise and local factors, such as local subsidence and uplift. Relative sea level rise is measured with respect to a specified vertical datum relative to the land, which may also be changing elevation over time.

Renewable energy

Energy resources that are naturally replenishing such as biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action.

Reservoir dredging

It is common for cities and municipalities to source the community’s water from open-air reservoirs. Sometimes these reservoirs will silt-in or become contaminated with material that drains from the surrounding area. Dredging is an efficient and effective way to continually keep these reservoirs clean.

Residence time

The average time spent in a reservoir by an individual atom or molecule. With respect to greenhouse gases, residence time refers to how long on average a particular molecule remains in the atmosphere. For most gases other than methane and carbon dioxide, the residence time is approximately equal to the atmospheric lifetime.

Resilience

A capability to anticipate, prepare for, respond to, and recover from significant multihazard threats with minimum damage to social well-being, the economy, and the environment.

Respiration

The process whereby living organisms convert organic matter to CO₂, releasing energy and consuming O₂.

Retention time

The time water, sludge, or solids are retained or held in a clarifier or sedimentation tank.

Return activated sludge (RAS)

(a) Settled activated sludge, returned from the bottom of final sedimentation clarifiers, to mix with incoming raw or primary effluent; (b) floated activated sludge, returned from the top of flotation clarifiers, to mix with incoming raw or primary effluent.

Reunification

A process to ensure that children are safely reunited with parents or legal guardians when an emergency occurs.

Riparian

It is an environment of, relating to, or situated on the banks of a river.

Rising sludge

Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is compacted, and then starts to rise to the surface, usually as a result of denitrification.

Risk management

In business, or science, or engineering, the forecasting and evaluation of public health, environmental, financial risks together with the identification of procedures to avoid or minimize their impact.

River dredging

The most common use for cutter suction dredge equipment. River projects vary in purpose. Some river dredging projects work to maintain adequate channel depths, while others are aimed at flood control and mitigation.

Robbing

It is an action of stealing nectar or honey by bees from other colonies, which occurs more often during a nectar dearth.

Rotary drum thickening

It is sludge preliminary concentration process for removal of water from dilute sludge using a rotary screen drum. In operation, polymer is mixed with dilute sludge, and the conditioned sludge is then passed through rotating screen drums, which separate the flocculated solids from water. Thickened sludge rolls out the end of the drums, while separated water decants through the screens.

Rotating biological contactor (RBC)

In an RBC system, a series of closely spaced circular polystyrene or polyvinyl chloride disks is partially submerged in wastewater. Biological growth (biomass) attached to the surface of the disks. The biomass is kept in aerobic conditions (if carbonaceous oxidation and nitrification are intended), or anoxic conditions (if denitrification is intended) by rotation of the disks. Aerobic RBC is opened, so biomass may utilize the oxygen in the air, while anoxic RBC for denitrification is normally closed to block off the air. The RBC effluent discharges to a clarifier (either a sedimentation clarifier or a flotation clarifier) for solid-water separation, returning sludge, wasting sludge, and clarifier effluent discharge.

Salmon

(a) A large edible fish that is a popular game fish, much prized for its pink flesh. Salmon mature in the sea but migrate to freshwater streams to spawn. (b) Salmon is the common name for several species of ray-finned fish in the family Salmonidae. Other fish in the same family include trout, char, grayling, and whitefish. Salmon are native to tributaries of the North Atlantic and Pacific Ocean. (c) Representatives of salmon are sockeye salmon, Atlantic salmon, Chinook salmon, Coho salmon, and pink salmon.

Salt water intrusion

Displacement of fresh or ground water by the advance of salt water due to its greater density, usually in coastal and estuarine areas.

Sample

A part of a larger whole or a single item of a group; a finite part or subset of a statistical population. A sample serves to provide data or information concerning the properties of the whole group or population.

Sampling

The process of obtaining a representative portion of the material of concern.

Sand and gravel dredging

It is an extremely common industry worldwide. Sand and gravel dredged from rivers or landlocked mines provide aggregate materials for building, construction, and infrastructure projects.

Sandfloat

It is combined circular dissolved air flotation and filtration (DAFF) clarifier designed by the Lenox Institute of Water Technology (LIWT) and manufactured by Krofta Engineering Corporation (KEC).

Sanitary landfill

Burying sludge or solid wastes to minimize nuisance conditions or public health problem is called sanitary landfill. Sludge and solid wastes are buried in layers, which are covered with fill material excavated at the site. Landfills must be located where nearby wells and groundwater supplies will not be contaminated by leachate from the landfill operation. Sludge landfills are generally separate from refuse landfills.

Sanitation

The development and application of measures for the sake of cleanliness and protecting health, especially the disposal of excreta and solid waste.

Scale, map

It is the ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground.

Scenarios

A plausible and often simplified description of how the future may develop based on a coherent and internally consistent set of assumptions about driving forces and key relationships.

Screen

A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform in size. It retains or removes objects larger than the openings. A screen may consist of bars, rods, wires, gratings, wire mesh, or perforated plates.

Sea surface temperature

The temperature in the top several feet of the ocean, measured by ships, buoys, and drifters.

Secondary effluent

The effluent from a secondary treatment step, which may be either (a) biological treatment, such as activated sludge aeration or equivalent plus secondary clarification, or (b) physicochemical treatment, such as chemical precipitation/coagulation plus secondary clarification. Secondary treatment step removes most of dissolved organic/inorganic pollutants from primary effluent. Since secondary clarification (either secondary sedimentation clarification or secondary flotation clarification) is the final step of secondary treatment, the secondary effluent is also the secondary clarification effluent.

Secondary flotation clarification

It is a unit process or unit operation for removal of the bio-oxidation process generated activated sludge, and/or the chemical precipitation/coagulation process generated chemical sludge using a secondary flotation clarifier.

Secondary flotation clarifier

A dissolved air flotation (DAF) reactor is used to float biological sludge (activated sludge) from biologically oxidized wastewater (such as aeration tank effluent) and/or chemical sludge from chemically coagulated /flocculated wastewater (such as flocculator effluent) by decreasing the sludge’s apparent density. DAF consists of saturating a portion or all of the wastewater feed, or a portion of recycled effluent with air at a pressure of 25 to 90 lb./square inch (gage). The pressurized wastewater is held at this pressure for 0.5 to 3 minutes in a retention tank and then released to atmospheric pressure to the flotation chamber. The sudden reduction in pressure results in the release of microscopic air bubbles, which attach themselves to suspended solids and other particles in the wastewater in the flotation chamber. This results in agglomeration, which, due to the entrained air, has greatly increased vertical rise rates of about 0.5 to 2 ft./min. The floated materials rise to the surface to form a froth layer (float). Specially designed scrapers or other skimming devices continuously remove the froth (or float). The retention time in the flotation chambers is usually about 20–60 minutes for rectangular flotation clarifier, and about 3–15 minutes for circular flotation clarifier using zero-horizontal velocity design. The effectiveness of dissolved air flotation depends upon the attachment of bubbles to the suspended solids, which are to be removed from the waste stream. The attraction between the air bubble and particle is primarily a result of the particle surface charge and bubble-size distribution. The more uniform the distribution of water and microbubbles, the shallower the flotation clarifier can be. Generally, the depth of effective flotation units is between 3 and 9 feet.

Secondary membrane clarification (or secondary membrane separation, or secondary membrane filtration)

A water-solid separation/clarification process uses membrane device instead of conventional sedimentation clarification in the secondary wastewater treatment step.

Secondary sedimentation clarification

It is a unit process or unit operation for removal of the bio-oxidation process generated activated sludge, and/or the chemical precipitation/coagulation process generated chemical sludge using a secondary sedimentation clarifier.

Secondary sedimentation clarifier

It is a tank used to settle the chemical precipitation/coagulation process generated chemical sludge, and/or the bio-oxidation process generated activated sludge for removing dissolved organic/inorganic substances from wastewater. The main objectives of a secondary sedimentation clarifier are removal of settleable chemical and/or biological sludge solids by settling them to the clarifier bottom. In a rectangular sedimentation clarifier, the wastewater flows from one end to the other and the settled sludge is moved to a hopper at on end, either by scrapers called “flights” set on parallel chains, or by a single bottom scraper set on a traveling bridge. In a circular sedimentation clarifier, the wastewater usually enters in the middle and flows toward the outside edge. Settled sludge is pushed to the hopper that is in the middle of the circular clarifier’s tank bottom.

Secondary treatment

It is a wastewater treatment step after primary treatment (either primary sedimentation clarification or primary flotation clarification). Secondary treatment may be either biological treatment (such as activated sludge aeration plus secondary clarification) or physicochemical treatment (such as chemical precipitation/coagulation plus secondary clarification) mainly for removing dissolved organic/inorganic pollutants from primary effluent.

Sediments

They are the materials that settle on the bottom of a waterway that has been transported from the surrounding area over time as a result of weathering and erosion.

Selector hydraulic retention time (HRT)

The given time it takes wastewater, including any return flows, to pass through a tank (selector).

Selector

A zone in a biological treatment process with specific environmental conditions that allow for the growth or lack of growth of certain microorganisms (such as an anoxic or anaerobic zone).

Seminar

Session designed to orient participants to new or updated plans, policies, or procedures through informal discussion.

Sensitivity

The degree to which a system is affected, either adversely or beneficially, by climate variability or change. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range, or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea level rise).

Septic

A condition produced by anaerobic bacteria. If severe, the wastewater produces hydrogen sulfide, turns black, gives off foul odors, contains little or no dissolved oxygen, and creates a high oxygen demand.

Sequencing batch exchanger (SBE)

A sequencing batch process involving the use of separate batch process steps in sequence of filling water/wastewater, reacting with ion exchanger, settling insoluble spent ion exchanger, discharging treated effluent, and recycling the settled spent ion exchanger for regeneration, resulting in removing ionic pollutants from water or wastewater. (US Patent 5,354,458).

Sequencing batch flotation (SBF)

A sequencing batch process (either biological or physicochemical) involving the use of separate batch process steps in sequence of filling water/wastewater, reacting with chemicals or biomass, floating light weight-insoluble flocs and/or biomass, discharging treated effluent, and wasting floated insoluble scums, for water or wastewater treatment is also called sequencing batch flotation (SBF) process. (US Patent 5,354,458).

Sequencing batch reactor (SBR), biological

A biological SBR system performs all the necessary functions of carbonaceous and nutrient removals in a single tank with variable water levels and timed aerobic aeration or anoxic mixing. This SBR system requires a minimum of three tanks and advanced automation equipment to control the cycle times and phases. The SBR control systems allow the operation to be configured to operate as almost any other suspended growth biological reactor by adjusting the cycle phases between fill phase, react phase (either aerobic aeration or anoxic mixing), separation phase (either sedimentation or flotation), and decant phase. The biological SBR system involving the use of flotation in the separation phase is invented by Dr. Lawrence K. Wang,, Dr. Lubomyr Kurylko, and Dr. Mu-Hao Sung Wang in 1994 (US Patent 5,354,458).

Sequencing batch reactor (SBR), physicochemical

A physicochemical SBR system performs all the necessary functions of organic and inorganic pollutants removals in a single tank with variable water levels and timed mixing, coagulation/flocculation, or clarification (either sedimentation or flotation). This SBR system requires a minimum of three tanks and advanced automation equipment to control the cycle times and phases. The SBR control system allows the operation to be configured to operate as almost any other suspended floc physicochemical reactor by adjusting the cycle phases among fill phase, react phase (chemical precipitation/coagulation, flocculation), separation phase (either sedimentation or flotation clarification), and decant phase. The physicochemical SBR system involving the use of either sedimentation or flotation in the separation phase is invented by Lawrence K. Wang,, Lubomyr Kurylko, and Mu-Hao Sung Wang in 1994 (US Patent 5,354,458).

Sewage

The used water and water-carried solids from homes that flow in sewers to a wastewater treatment plant. The preferred term is “wastewater.”

Shelter-in-place

A procedure to keep you safe by remaining inside. It involves selecting an interior room or area in which to take refuge. Where you shelter depends on the type of hazard or threat.

Short-circuiting

Shortening of hydraulic detention time, such as when plant flow exceeds design flow.

Short ton

Common measurement for a ton in the United States. A short ton is equal to 2000 lbs. or 0.907 metric tons.

Short-circuiting

A condition that occurs in tanks or basins when some of the water travels faster than the rest of the flowing water. This is usually undesirable, since it may result in shorter contact, reaction, or settling times in comparison with the theoretical (calculated) or presumed detention times.

Shredding

It is a unit operation for reducing the particle size of objects or debris in the influent wastewater, also termed grinding or comminuting. These devices may be installed with a screen directly in the wastewater flow or separately out of the wastewater flow, with the shredded particles returned to the flow downstream of the screen. Only those shredding and grinding devices that are installed directly in the influent channel are termed comminuting devices.

Sidestreams

Sources of inflow from within the wastewater treatment facility, such as supernatant return from digesters, centrate from centrifuge thickening, filtrate from filter presses, etc. These sidestreams may be high in solids, BOD, or nutrients and may add to the plant organic or hydraulic loading.

Single-sludge activated sludge system

It is a biological activated sludge process system involving the use of one suspended activated sludge solids going through aerobic and anoxic zones for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal. The single-sludge activated sludge system is commonly a continuous flow system using sedimentation clarification. Lenox Institute of Water Technology (LIWT) has developed three innovative single-sludge activated sludge systems all for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal: (a) continuous flow single sludge system using flotation clarification; (b) sequencing batch reactors (SBR) using sedimentation for carbonaceous removal and nutrient removal; and (c) SBR using flotation for carbonaceous removal and nutrient removal.

Sink

Any process, activity, or mechanism, which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas or aerosol from the atmosphere.

Sintering

Using heat or pressure to form a solid mass of material, without melting the material to the point of liquefying.

Sludge

(a) The settleable solids separated from liquids during processing. (b) The deposits of foreign material on the bottoms of streams or other bodies of water.

Sludge age (SA)

SA is the length of time a particle of activated sludge stays in the biological treatment plant, measured in days. In a biological phosphorus removal plant, sludge age is the amount (pound or kilogram) of mixed liquor suspended solids in all the biological reactors divided by the suspended solids withdrawn from the system per day (pound per day of waste activated sludge, or kilogram per day of waste activated sludge).

Sludge dewatering

Sludge dewatering is the second step of sludge handling, after sludge thickening. Sludge dewatering is required for all facilities that do not dispose of their sludge in liquid form. It is a physical (mechanical) process to reduce the moisture content of sludge. The purpose is to reduce sludge volume, in turn, to reduce subsequent sludge digestion costs and/or final sludge disposal (land disposal or incineration) costs. Dewatering is usually required prior to sludge incineration. There are a variety of dewatering processes available: (a) vacuum filtration; (b) centrifuge; (c) belt filter press; (d) plate and frame press; (e) sludge drying beds or infrared sludge dryer; (f) sludge lagoons.

Sludge digestion

The process of changing organic matter in sludge into a gas or liquid or a more stable solid form. These changes take place as microorganisms feed on sludge in anaerobic (more common) or aerobic digesters.

Sludge dryer, infrared

It is a sludge dewatering process using regular direct radiant energy from infrared heating elements. Dewatered sludge is transferred from the dewatering equipment to the dryer by a conveyor belt. The sludge then drops into the augers, where the auger blades agitate the sludge, while infrared heating elements heat the sludge. This process then repeats once the sludge is dropped into the secondary drying zone.

Sludge dryer, microwave

It is a new sludge dewatering process developed by Lawrence K. Wang of the Lenox Institute of Water Technology involving the use of microwave energy from a microwave dryer. Dewatered sludge is transferred from the dewatering equipment to the dryer by a conveyor belt. The sludge then drops into the augers, where the auger blades agitate the sludge, while microwaves heat and dewater the sludge. This process then repeats once the sludge is dropped into the secondary drying zone.

Sludge drying beds

It is a sludge dewatering process using solar energy to evaporate water from the sludge slurries.

Sludge handling

It includes every required processes or management regarding waste sludge, such as sludge thickening, sludge dewatering, sludge digestion, sludge storage, sludge transportation, sludge disposal, etc.

Sludge lagoons

It is an earthen basin used for holding and dewatering sludge slurries by solar energy.

Sludge thickening and dewatering combined, belt filter press

Conditioned sludge is first placed on a gravity drainage section where it is allowed to thicken. In this section, the bulk of the free water is removed from the sludge by gravity. On some units, this section is equipped with a vacuum assist, which enhances drainage and may help to reduce odors. Following gravity drainage, pressure is applied in a low-pressure section, where sludge is squeezed between opposing porous cloth belts. On some units, the low-pressure section is followed by a high-pressure section where the sludge is subjected to shearing forces that induce the release of additional quantities of water from the sludge. The final dewatered sludge cake is removed from the belts by scrapper blades.

Sludge thickening/dewatering centrifuge, basket centrifuge

They are suitable for small plants. It is a semibatch type operation. Sludge cake is collected on the sides of the spinning bowl, while the centrate (dilute effluent stream from the centrifuge) overflows the bowl rim. Once solids have built up to a maximum thickness, the feed sludge is stopped and scrapper blades peel the sludge from the walls. The process is then resumed.

Sludge thickening/dewatering centrifuge, solids bowl centrifuge

Sludge is fed at a constant flowrate into the rotating bowl where it is separated into a dense cake and a dilute stream called centrate. The units can be used with no prior chemical conditioning, but solids caputer and centrate quality are improved considerably when the sludge is conditioned with polymer.

Sludge thickening

Sludge thickening is the first step of sludge handling. It is employed prior to subsequent sludge dewatering processes to increase the efficiency of the sludge dewatering equipment. There are at least five types of sludge thickening processes: gravity thickening, flotation thickening, centrifuge thickening, gravity belt thickening, and rotary drum thickening.

Sludge volume index (SVI)

SVI is the ratio of the volume (in mL) of sludge settled from a 1000 mL sample in 30 minutes to the concentration of mixed liquor (in mg/L) multiplied by 1000. It indicates settling capabilities, compaction, and it is an indication of filamentous organism overgrowth and several other indicators of process problems.

Slurry

It is a term used to describe the mixture of solids with a liquid (typically water). In dredging, these solids can include silt, sand, gravel, clay, or coal.

Snowpack

A seasonal accumulation of slow-melting snow.

Sodium hypochlorite

It is a liquid sodium hypochlorite solution to be used as a disinfectant for water or wastewater disinfection.

Soil carbon

A major component of the terrestrial biosphere pool in the carbon cycle. The amount of carbon in the soil is a function of the historical vegetative cover and productivity, which in turn is dependent in part upon climatic variables.

Solar radiation

Radiation emitted by the Sun. It is also referred to as short-wave radiation. Solar radiation has a distinctive range of wavelengths (spectrum) determined by the temperature of the Sun.

Solid wastes

A solid waste is defined by the US Environmental Protection Agency (USEPA) as the following: Any garbage, refuse, sludge from a waste treatment plant, water supply treatment plant or air pollution control facility, and other discarded materials including solid, liquid, semisolid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations and from community activities Sect.6903(27). The regulatory definition is found at 40CFR261.2(a)(1). A solid waste is defined by the US regulation as any “discarded material” not expressly excluded by the US regulations. A material is considered “discarded” if it is “abandoned,” “recycled,” or “considered inherently waste-like.” Accordingly, the discarded, abandoned, recycled, or waste-like materials generated from a laboratory facility are all considered to be solid wastes.

Solidification/stabilization (S/S)

The process utilizes chemically reactive formulations that, together with the water and other components in sludges and other aqueous hazardous wastes, form stable solids.

Solids retention time (SRT)

The theoretical length of time, usually in days, that solids are retained in an aeration basin, clarifier, or other structure. SRT is used to calculate wasting rates.

Soluble BOD (SBOD)

Soluble BOD is a sample that has been filtered through a 0.45μm filter. Soluble BOD includes volatile fatty acids (VFAs) and organic material that will readily ferment to create more VFAs in an anaerobic selector.

Soluble

Dissolved in a solution and more readily available for biochemical or chemical reactions. For instance, soluble BOD or soluble COD is readily available as food to microorganisms in a biochemical reaction. Soluble BOD includes volatile fatty acids (VFAs) and organic material that are readily available to microorganisms in a biological process.

Solution

(a) A liquid (solvent) that contains a dissolved substance (solute). (b) A liquid mixture of dissolved substances. In a solution, it is impossible to see all the separated parts.

Solvent

A liquid used to dissolve another substance.

Spatial Analysis

It is the process of modeling, examining, and interpreting model results. Spatial analysis is useful for evaluating suitability and capability, for estimating and predicting, and for interpreting and understanding.

SPDES permit

State Pollutant Discharge Elimination System (SPDES) permit is each State’s regulatory agency document issued by either a state agency, which is designed to control all discharges of pollutants from all point sources and storm water runoff into US waterways. A State’s treatment plant that discharges to a State’s surface water will have an SPDES permit.

Spectrophotometer

(a) Meter that uses a specific wavelength of light to measure light absorption in a sample; used for phosphorus, ammonia, nitrite, and nitrate analyses. (b) A spectrophotometer is an instrument designed for physical sample analysis via full spectrum color measurement. By providing wavelength-by-wavelength spectral analysis of a sample’s reflectance, absorbance, or transmittance properties, it produces precise data beyond that observable by the human eye. Spectrophotometers offer a higher level of flexibility and versatility than colorimeters due in part to the fact that they offer multiple illuminant/observer combinations and are capable of measuring metamerism, identifying colorant strength, analyzing a comprehensive range of sample types, and giving users a choice between including or excluding specular reflectance to account for geometric attributes. Full spectrum analysis also provides for greater specificity, potentially identifying color differences missed by colorimeters.

Spoils, dredging

It is the name applied to both beneficial and nonbeneficial discharged dredged material—also referred to as discharge, fill, or deposit.

Spuds, dredge

They are large steel cylinders located at the end of the dredge ranging from 20′ (6 m) to 100′ (30 m) in height. Spuds hold the dredge in place during operation and are used to advance the dredge by “walking” it forward.

Standard solution

A solution containing a known concentration of analytes, prepared and verified by a prescribed method or procedure and used routinely in an analytical method.

Storm sewer

A separate pipe, conduit, or open channel (sewer) that carries runoff from storms, surface drainage, and street wash, but does not include domestic and industrial wastes.

Storm surge

An abnormal rise in sea level accompanying a hurricane or other intense storm, whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone.

Stratosphere

Region of the atmosphere between the troposphere and mesosphere, having a lower boundary of approximately 8 km at the poles to 15 km at the equator and an upper boundary of approximately 50 km. Depending upon latitude and season, the temperature in the lower stratosphere can increase, be isothermal, or even decrease with altitude, but the temperature in the upper stratosphere generally increases with height due to absorption of solar radiation by ozone.

Streamflow

The volume of water that moves over a designated point over a fixed period of time. It is often expressed as cubic feet per second (ft3/sec).

Structural elements

Any component of the building whose primary function is to support the dead load (e.g., building, roof).

Structured Query Language (SQL)

It is a syntax for defining and manipulating data from a relational database. Developed by IBM in the 1970s, it has become an industry standard for query languages in most relational database management systems.

Struvite

It is magnesium ammonium phosphate (MgNH₄PO₄(H₂O)₆). Struvite forms hard, very insoluble, white, yellowish-white, or brownish-white crystals.

Subnatant

The water or liquid remaining below a floated sludge (float) after flotation.

Subsiding/subsidence

The downward settling of the Earth’s crust relative to its surroundings.

Substrate

The food or chemical substance on which organisms depend for growth. The organic matter in wastewater (as measured by the BOD₅ test) is a substrate for the microorganisms in a biological process. For instance, in biological phosphorus removal systems, volatile fatty acids are a readily available substrate used by phosphorus-accumulating organisms (PAOs).

Sulfate aerosols

Particulate matter that consists of compounds of sulfur formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. Sulfate aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes like Mt. Pinatubo. Sulfate aerosols can lower the Earth’s temperature by reflecting away solar radiation (negative radiative forcing). General Circulation Models, which incorporate the effects of sulfate aerosols more accurately, predict global temperature variations.

Sulfur hexafluoride (SF₆)

A colorless gas soluble in alcohol and ether, slightly soluble in water. A very powerful greenhouse gas used primarily in electrical transmission and distribution systems and as a dielectric in electronics. The global warming potential of SF6 is 22,800. This GWP is from the IPCC’s Fourth Assessment Report (AR4).

Super

It is a part of commercial or other managed beehive that is used to collect surplus honey. Normally, it is placed over or above the brood chamber.

Supernatant

Liquid removed from settling sludge. Supernatant commonly refers to the liquid between the sludge on the bottom of an anaerobic digester and the scum on the surface. The liquid is usually returned to the influent wet well or to the primary clarifier.

Supracell

It is a circular dissolved air flotation (DAF) clarifier designed by the Lenox Institute of Water Technology (LIWT) and manufactured by Krofta Engineering Corporation (KEC).

Surface water

Surface water is water on the surface of continents such as in a river, lake, or wetland. It can be contrasted with groundwater and atmospheric water. Nonsaline surface water used is replenished by precipitation and by recruitment from ground-water.

Surfactant

A surface active compound that lowers the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, etc.

Surplus honey

It is the honey removed from the hive, which exceeds what is needed by bees for their own use.

Suspended solid

Solids that either float on the surface or are suspended in water, wastewater, or other liquids, and which are largely removable by laboratory filtering.

Suspended-growth biological processes

In a suspended-growth biological process system, biomass or microorganisms are suspended in the biological reactors for aerobic and/or anoxic biochemical reactions. They include all kinds of activated sludge processes as well as oxidation ditch process, such as (a) conventional activated sludge process using diffused aeration; (b) conventional activated sludge process using mechanical aeration; (c) high rate activated sludge process using diffused aeration; (d) pure oxygen activated sludge process using covered reactor; (e) pure oxygen activated sludge process using uncovered reactor; (f) extended aeration activated sludge process with nitrification; (g) activated sludge process separate reactors for carbonaceous oxidation, nitrification, and denitrification; (h) single sludge activated sludge process for carbonaceous oxidation, nitrification, and denitrification; (i) sequencing batch reactor (SBR); (j) membrane bioreactor (MBR); (k) oxidation ditch process; (l) aerated lagoon, etc. The effluent of the suspended-growth bioreactor (aeration tank, or oxygenation tank, or mixing tank) discharges to a solid-water separator (sedimentation clarifier, flotation clarifier, or membrane filter) for additional processing.

Swarm

It represents a large number of worker bees and drones, and usually the old queen leaves the parent colony to establish a new colony.

Swarming

It is the natural process of honey bee reproduction at colony level.

Tabletop exercise

A discussion-based exercise intended to stimulate discussion of various issues regarding a hypothetical situation. Tabletop exercises can be used to assess plans, policies, and procedures or to assess types of systems needed to guide the prevention of, protection against, response to, or recovery from a defined incident. Tabletop exercises are typically aimed at facilitating understanding of concepts, identifying strengths and shortfalls, and/or achieving a change in attitude. Participants are encouraged to discuss issues in depth and develop decisions through slow-paced problem-solving rather than the rapid, spontaneous decision-making that occurs under actual or simulated emergency conditions. Tabletop exercises can be breakout (i.e., groups split into functional areas) or plenary (i.e., one large group).

Tailings

It is a maintenance operation for reclaiming or eliminating mine tailings through dredging that supports efficient mine operations. Typical sectors include iron ore, gold, and oil sands where reclamation of tailings can have a positive return on investment.

Technology

It is professional field involving the application of known knowledge as a “tool” that extends human capability (e.g., from hammers to the internet).

Teragram

1 trillion (1012) grams = one million (106) metric tons.

Terminal elevation, dredge

It is the vertical height above the centerline of the dredge pump and the final point of discharge.

Tertiary flotation clarification

A dissolved air flotation clarification process, which is used for advanced or tertiary treatment with a main purpose of nutrient removal or wastewater renovation.

Tertiary membrane clarification (or tertiary membrane separation, or tertiary membrane filtration)

A water-solid separation/clarification process uses membrane device instead of conventional sedimentation clarification in the tertiary wastewater treatment step, such as nitrification and denitrification.

Tertiary treatment

It is a wastewater treatment step after secondary treatment, meaning tertiary treatment is for treating the secondary effluent in that most of organic substances have been removed. Normally, tertiary treatment includes nitrogen removal processes, phosphorus removal processes, granular activated carbon, granular media filtration, membrane filtration, and postaeration.

Theme, ArcView

An ArcView theme stores map features as primary features (such as arcs, nodes, polygons, and points) and secondary features such as tics, map extent, links, and annotation. A theme usually represents a single geographic layer, such as soils, roads, or land use.

Thermal discharge

An industrial, agricultural, or commercial discharge of heated liquid (such as wastewater, or gas, or steam from a factory) into natural waters or air at a temperature harmful to the environment.

Thermal expansion

The increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the ocean volume, which leads to an increase in sea level.

Thermal stabilization

A heating process for metal incorporation into certain stable products.

Thermohaline circulation

Large-scale density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic, the thermohaline circulation consists of warm surface water flowing northward and cold deep water flowing southward, resulting in a net poleward transport of heat. The surface water sinks in highly restricted sinking regions located in high latitudes.

Thickener, flotation

A tank or basin in which liquid sludge is held for a period of time during which most of the lighter air-sludge flocs float to the liquid surface as the concentrated-thickened sludge and very small amount of the very heavier solids will settle to the tank bottom.

Thickener, gravity

A tank or basin in which liquid sludge is held for a period of time during which most of the heavier solids settle to the tank bottom as the concentrated-thickened sludge and very small amount of the lighter solids will float to the water surface as the scum.

Thickening, sludge

Sludge thickening is employed prior to subsequent sludge dewatering processes to increase the efficiency of the sludge dewatering equipment. There are at least five types of sludge thickening processes: gravity thickening, flotation thickening, centrifuge thickening, gravity belt thickening, and rotary drum thickening.

Threat

Natural, technological, or human-caused occurrence, individual, entity, or action that has or indicates the potential to harm life, information, operations, the environment, and/or property.

Thunderstorm

A storm with thunder and lightning, often accompanied by rain or hail.

Tidal rivers

(a) A tidal river is a river, or more typically a stretch of a river, whose flow and level is influenced by tides; (b) a river that enters a sea or estuary and is thus affected by tides.

Tornado

A violent, rotating column of air that extends between, and is in contact with, the ground and a cloud.

Total Kjeldahl nitrogen (TKN)

The combined amount of organic and ammonia nitrogen determined by a laboratory analysis.

Total nitrogen (TN)

All forms of nitrogen including ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, and organic nitrogen.

Total phosphorus (TP)

All forms of phosphorus, including orthophosphate, polyphosphates, and organic phosphorus.

Toxic

A substance which is poisonous to a living organism.

Toxicity

The relative degree of being poisonous or toxic. A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms.

Trace gas

Any one of the less common gases found in the Earth’s atmosphere. Nitrogen, oxygen, and argon make up more than 99 percent of the Earth’s atmosphere. Other gases, such as carbon dioxide, water vapor, methane, oxides of nitrogen, ozone, and ammonia, are considered trace gases. Although relatively unimportant in terms of their absolute volume, they have significant effects on the Earth’s weather and climate.

Transpiration

Similar to Evapotranspiration.

Tropical storm

A severe storm that develops over tropical seas with winds from 39 to 73 miles per hour.

Troposphere

The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and “weather” phenomena occur. In the troposphere, temperatures generally decrease with height.

Tsunami

Enormous waves caused by underwater disturbances such as earthquakes.

Tundra

A treeless, level, or gently undulating plain characteristic of the Arctic and sub-Arctic regions characterized by low temperatures and short growing seasons.

Turbid

Having a cloudy or muddy appearance.

Two-stage DAF

A series of two consecutive dissolved air flotation treatment using different chemicals or operational conditions.

Two-stage treatment

A series of two consecutive water or wastewater treatment using different chemicals, operational conditions, or even different unit processes.

Ultraviolet radiation (UV)

(a) Most UV disinfection units are constructed with an array of VU lamps installed in a water, wastewater, or air channel, for water disinfection, wastewater disinfection, or air disinfection, respectively. A proper dosage of UV radiation has shown to be an effective bactericide and virucide while not contributing to the formation to toxic disinfection by-products. However, certain compounds may be altered by UV radiation. Because the effective distance of UV light is very limited, most UV disinfection occurs when the light penetration depth can be minimized, termed the thin film approach. The term “thin film” refers to the separation distance between the UV tubes. (b) The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition. Most ultraviolet radiation is blocked by Earth’s atmosphere, but some solar ultraviolet penetrates and aids in plant photosynthesis and helps produce vitamin D in humans. Too much ultraviolet radiation can burn the skin, cause skin cancer and cataracts, and damage vegetation.

Urban runoff

Storm water from city streets and adjacent domestic or commercial properties that may carry pollutants of various kinds into the sewer systems and from there to rivers, lakes, or oceans.

Vacuum filtration

This sludge dewatering process consists of a cylindrical drum which rotates partially submerged in a vat of sludge. The filter drum is divided into compartments by partitions or seal strips. A vacuum is applied between the drum deck and filter medium, causing filtrate to be removed and filter cake to be retained on the medium during the pickup and cake drying cycle. The filter medium may be a cloth made of natural or synthetic fibers, stainless steel wire mesh, or coil springs. Dewatered sludge is ordinarily removed by a fixed scraper blade.

Vector

(a) In environmental science, an organism, typically a biting insect or tick, that transmits a disease or parasite from one animal or plant to another. (b) A quantity having direction as well as magnitude, especially as determining the position of one point in space relative to another. (c) In mathematics and physics, a vector is an element of a vector space. For many specific vector spaces, the vectors have received specific names, which are listed below. Historically, vectors were introduced in geometry and physics before the formalization of the concept of vector space.

Vegetable oil

An oil derived from plants, e.g., canola oil, olive oil, sunflower oil.

Ventilated improved pit latrine (VIP)

It is a pit latrine with a black vent pipe going from the pit to above the superstructure with a fly screen on top. VIP latrines have the advantage over simple pit latrines of removing flies and odors if designed, built, and used properly.

Volatile fatty acids (VFAs)

Fatty acids containing fewer carbon atoms, and are dissolvable in water. When organic material undergoes fermentation reactions, smaller and more readily available organic molecules are formed known as volatile fatty acids (VFAs). VFAs typically found in wastewater are acetic acid (acetate) and propionic acid. VFAs provide the food for PAOs.

Volatile solids

Those solids in water, wastewater, or other liquids that are lost on ignition of the dry solids at 550 ° C.

Volcano

A vent in the Earth that, when pressure builds and it erupts, releases dangerous molten rock and gases.

Vulnerability

The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate variation to which a system is exposed; its sensitivity; and its adaptive capacity.

Warning

A notice issued when a hazardous weather event is occurring, is imminent, or has a very high probability of occurring. A warning is used for conditions posing a threat to life or property.

WASH

It is an acronym that means Water, Sanitation, and Hygiene. Access to WASH usually includes safe water, appropriate sanitation, and hygiene education. Adequate access to WASH can greatly reduce water-borne diseases in a community.

Waste activated sludge (WAS)

Solids removed/wasted from a biological process, such as activated sludge process, to prevent an excessive buildup in the system.

Waste disposal

Removing and destroying or storing damaged, used or other unwanted domestic, agricultural or industrial products and substances for final disposal by burning, burial at landfill sites or at sea, and recycling.

Waste management

Waste management includes the activities and actions required to manage waste from its inception to its final disposal. This includes the collection, transport, treatment, and disposal of waste, together with monitoring and regulation of the waste management process.

Wastewater renovation

Treatment of wastewater to a degree that the wastewater becomes a useful water resource.

Wastewater

(a) Water that has been used and contains dissolved or suspended waste materials. (b) The used water and solids from a community that flow to a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. The term “sewage” usually refers to household wastes, but this word is being replaced by the term “wastewater.”

Watch

A notice used when the risk of a hazardous weather event has increased significantly, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so that those who need to set their plans in motion can do so.

Water quality management

The water-quality-related activities include the systematic collection of physical, chemical, and biological information, and the analysis, interpretation, and reporting of those measurements, according to a preplanned design and structure.

Water quality

It refers to the chemical, physical, biological, and radiological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species, or to any human need or purpose.

Water reclamation

It is a process consisting of proper wastewater treatment to a degree that the treated water can be directly or indirectly reused/recycled.

Water resources

Water in various forms, such as rain, snow, ice, clouds, surface water, groundwater, reclaimed water, or reused water that is potentially useful for domestic, agricultural, industrial, commercial, or recreational applications.

Water vapor

The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration through direct emissions, it contributes to the enhanced greenhouse effect, because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor also affects the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation.

Weather

Atmospheric condition at any given time or place. It is measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. In most places, weather can change from hour to hour, day to day, and season to season. Climate in a narrow sense is usually defined as the “average weather,” or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. A simple way of remembering the difference is that climate is what you expect (e.g. cold winters) and “weather” is what you get (e.g., a blizzard).

Weir

A wall or plate placed in an open channel and used to measure the flow of water. The depth of the flow over the weir can be used to calculate the flow rate, or a chart or conversion table may be used.

Wet bulb temperature

The temperature measured by an ordinary thermometer as a thin film of water on the thermometer is evaporated into a surrounding air stream.

Wet infrastructure

It is the spectrum of water-related infrastructures relating to potable water supply, wastewater treatment, resources recovery, water storage, water resource management, flood management, coastal restoration, hydropower, and renewable energy facilities.

Wet oxidation

A method of treating or conditioning sludge before the water is removed. Compressed air is blown into the sludge; the air and sludge mixture is fed into a pressure vessel where the organic material is stabilized.

Wet well

A compartment or tank in which wastewater is collected. The suction pipe of a pump may be connected to the wet well or a submersible pump may be located in the wet well.

Winter storm

A weather event resulting from low temperatures that can include extreme low temperatures, strong winds, and precipitation like snow, sleet, and ice.

Worker bee

It is a female bee with undeveloped reproductive organ; the majority of the honey bees in a colony are worker bees, and they do all the work in the colony except laying fertile eggs. The worker honey bees visit flowers to obtain nectar and pollen as their food, and construct the waxy combs made from secretions of the wax glands. The worker bees tend the eggs and larvae as well as feed the queen and carry away the eggs produced by the queen.

Workshop

A type of training focused on increased participant interaction and achieving or building a product (e.g., plans, policies). A workshop is typically used to test new ideas, processes, or procedures; train groups in coordinated activities; and obtain consensus. Workshops often use breakout sessions to explore parts of an issue with smaller groups.

XRD analysis

A technique can provide both qualitative and quantitative information on the phases in a tested sample.

Zoogleal mass

Jelly-like masses of bacteria found in both the trickling filter and activated sludge processes.