Classic Cases of Integrated Rural Domestic Sewage Treatment

Abstract

Rural sewage treatment is essential for Baiyangdian ecological environment governance according to Baiyangdian ecological environment governance and protection planning (2018–2035) released by Hebei, China in Jan. 2019.

5.1 A Rural Domestic Sewage Treatment Case in Xiong’an New District, China

5.1.1 Project Overview

Features: Centralized Treatment on a large scale with high requirements for treated water

Construction Time: November 2019

Construction Scale: 200 m³/d

Project objective: The quality of treated water shall conform with the discharge standard for the key control area set by the Pollutant Discharge Standard in Daqing River Basin (GB 18918-2018), as shown in Table 5.1.

Table 5.1 Engineering design for the quality of domestic sewage and treated water

5.1.2 Project Background

Rural sewage treatment is essential for Baiyangdian ecological environment governance according to Baiyangdian ecological environment governance and protection planning (2018–2035) released by Hebei, China in January 2019. This project is one of the pioneering projects for the integrated and comprehensive treatment of rural sewage, garbage, toilets, and other environmental problems in Baiyangdian, Xiong’an New Area, China (Sewage Treatment Process Technical Route and Integrated Technology Approach for Xiong’an New Area Decentralized Villages).

The project is located in the east of Anxin County, Baoding, Hebei, China, with an annual average temperature of 13.4 °C. The average temperatures in January and July are − 4.3 °C and 26.4 °C, respectively. With roughly 1,530 households in the village where the project is located, the registered population is 4,325, of which, about 1/3 are migrant workers. There are six flushing public toilets in the village, with the coverage of household toilets reaching 1/3. Daily water supply time is about 6 h, from 6:30 to 9:30 and from 16:30 to 18:00, with 1–2 h more supply time for weddings and funerals. With tap water meters installed in each household, the water charge is performed as per the actual consumption. The project serves more than 2,570 residents.

5.1.3 Treatment Scheme

Given that the project is located in an environmentally sensitive area with strict discharge standards, the improved Bardenpho-MBBR integrated sewage treatment process with outstanding denitrification and phosphorus removal was selected. The process flow is shown in Fig. 5.1, with parameters of the integrated processing equipment shown in Table 5.2. Domestic sewage is discharged into the lifting well through the collection pipe network, which then flows through the grid channel, the sand settling tank, and the equalization tank successively. After that, treated water is lifted to the integrated equipment via the lifting pump for biochemical treatment, and is discharged after reaching the standard. The excess biochemical sludge is delivered out for disposal upon being temporarily stored in the sludge tank. The ground integrated treatment equipment is selected for this project, and is covered with a thermal insulation layer to maintain the water temperature and efficiency of biochemical treatment in view of low temperature in winter. And the operating cost is 1.2 yuan/m³ (excluding the labor cost).

Fig. 5.1

Process flow of domestic sewage treatment in a village in Xiong’an New Area, China

Table 5.2 Parameters for modified Bardenpho-MBBR process integrated equipment

5.1.4 Treatment Effect

The improved Bardenpho-MBBR sewage treatment process can achieve the project objective with a satisfactory treatment effect. The treated water met the discharge limit requirements of the key control areas in the Pollutant discharge standard of Daqing River basin (DB13/2795-2018). Outstanding denitrification performance can be achieved with the NH₃–N of < 1 mg/L and TN of 6–10 mg/L under extremely low-temperature conditions in winter (with the water temperature of 7–8 ℃). The site image is shown in Fig. 5.2.

Fig. 5.2

The site of a rural domestic sewage treatment case in Xiong’an New Area, China

5.1.5 Tips for Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation and process operation.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. The treatment efficiency can be improved by switching the water inlet mode by segment or adding a carbon source when the C/N ratio of domestic sewage is low.

• d. The quality and quantity of domestic sewage in the project fluctuated greatly, which exerted a large impact on the treatment efficiency of the equipment. Hence, it is imperative to ensure the normal operation of the lift pump in the equalization tank and control the liquid level of the equalization tank, avoiding the long-time operation of equipment with water volume exceeding the design criteria.

• e. When the devices should be shut down for a long time due to special reasons, electrical facilities such as the air pump, water pump, and electric control cabinet should be regularly maintained to ensure that they can be started normally at any time.

• f. The rest should refer to the operation and maintenance tips of the improved Bardenpho-MBBR sewage treatment process (3.2.6).

5.2 A Rural Domestic Sewage Treatment Case in Kaifeng, Henan, China

5.2.1 Project Overview

Features: Household/Joint Household Treatment Mode

Construction Time: August 2019

Construction scale: Covering seven administrative villages, serving more than 5000 residents. Project objective: The quality of treated water shall be in conformity with the third level criteria of the Discharge standard of pollutants for rural sewage treatment plants (DB41/1820-2019), as shown in Table 5.3.

Table 5.3 Engineering design for the quality of domestic sewage and treated water

5.2.2 Project Background

The rural toilet revolution is highlighted in the “Three-Year Action Plan for Rural Living Environment Improvement”. This was a demonstration project for the rural toilet revolution in Kaifeng, Henan, China, covering seven administrative villages, roughly 1000 households with approximately 5000 residents. The level III discharge criteria of the Discharge standard of pollutants for rural sewage treatment plants of Henan, China (DB41/1820-2019) was implemented. The following problems are seen in the rural domestic sewage treatment in this project:

• a. Difficulty to collect domestic sewage in a centralized manner. Domestic sewage cannot be collected in a centralized manner due to the incomplete toilet construction. Since there is neither a sewage pipe nor a supporting sewage treatment plant in most of the villages, domestic sewage is usually directly discharged into nearby rivers without any treatments.

• b. The sewage is incompletely collected, failing to attach importance to grey water treatment. The septic tanks in some farming households only have access to the sewage from the toilets, failing to collect the washing sewage, bathing sewage and kitchen sewage. The incomplete “four water” collection leads to low sewage treatment rate and pollution in the surrounding environment. Hence, the toilet revolution should be improved.

5.2.3 Treatment Scheme

The project is a supporting project for the toilet revolution, which is configured with a flexible selection of the single household/joint household treatment mode. And its integrated equipment has both the functions of sewage collection and treatment. High installation cost is a major problem in the single household/joint household sewage treatment. Given that installation and construction requirements are low, the mode of government organization, enterprise guidance, and farmer installation should be adopted in the project as it can effectively lower construction costs, boost farming household’s participation, and promote their understanding of equipment operation, environmental remediation as well as hygiene and safety.

Multi-stage A/O biological contact oxidation integrated process equipment characterized by strong resistance to impact load was adopted in the project. The process flow of the equipment is presented as below. Domestic sewage enters the equipment through gravity flow. Then it flows through the multi-stage anoxic zone (removal of organic matters, denitrification) and multi-stage aerobic zone (filling with biomass increasing sponge carrier to remove organic matters and ammonia nitrogen) in turn after the pretreatment in the septic zone (solid–liquid separation, and anaerobic fermentation). At last, it is sedimented in the sedimentation zone. The treated water can be directly discharged or flowed into the recycled tank for irrigation. Equipment parameters are shown in Table 5.4. The equipment can be used behind a septic tank (Fig. 5.3), or in scenarios without a septic tank in combination with multiple devices. The construction cost of the project is 5000 yuan/household, and the operating cost is 0.2 yuan/m³ (excluding the labor cost).

Table 5.4 Parameters for multi-stage A/O biological contact oxidation integrated single-tank equipment

Fig. 5.3

Process flow of a rural domestic sewage treatment project in Kaifeng, Henan, China

5.2.4 Treatment Effect

The project can effectively achieve the engineering objective. The integrated equipment yields favorable treatment effect, and the quality of treated water can stably reach the level III discharge criteria of the Discharge standard of water pollutants for rural sewage treatment plants of Henan, China (DB41/1820-2019). The site picture is shown in Fig. 5.4.

Fig. 5.4

The site of a rural domestic sewage treatment case in Kaifeng, Henan, China

5.2.5 Tips for Operation and Maintenance

• a. The dual mode of “daily maintenance + professional maintenance” is adopted. Farming households are responsible for routine maintenance such as domestic sewage control, blockage treatment, and normal power supply, while professional technicians are responsible for professional maintenance such as pump cleaning, water quality monitoring, equipment commissioning, mud pumping, and equipment maintenance.

• b. Operation and maintenance should be performed to ensure that facilities are in a stable power supply state for a long time due to the unique operating condition of the household facility (directly facing specific users, and the power is from the corresponding user). Otherwise, it will seriously affect the actual treatment effect of the facilities.

• c. The integrated facility should be dredged regularly, in general, once a year.

• d. The buried type equipment is adopted in this project. If the facility is submerged under extreme weather (such as heavy rain), the facility function will be restored through dredging after the normal weather.

5.3 A Rural Domestic Sewage Treatment Case in Liyang, Jiangsu, China

5.3.1 Project Overview

Features: Small-scale centralized treatment with high requirements for treated water

Construction time: July 2021

Construction scale: 20 m³/d

Project objective: The quality of treated water shall be in conformity with the Pollutant discharge standard of water for municipal sewage treatment plant (GB 18918-2002) (Table 5.5).

Table 5.5 Engineering design for the quality of domestic sewage and treated water

5.3.2 Project Background

Jiangsu is one of the earliest provinces in China to perform rural sewage treatment, with some areas achieving full coverage of rural sewage treatment. The total investment in the rural domestic sewage comprehensive treatment project in Liyang, Jiangsu, China, was estimated to be roughly 1.3 billion yuan. The project realizes comprehensive treatment of domestic sewage in 935 key villages in Liyang, Jiangsu, China, involving 1 street, 150 administrative villages, and 935 natural villages in 10 designated towns, and 91,130 beneficiary households.

The project involves the rural domestic sewage treatment in four towns, with the utilization of 155 sets of integrated treatment equipment in total, of which 110 sets of equipment conform to the treated water reaching the Level I B criteria of GB18918-2002, while 45 sets following the Level I A criteria of GB18918-2002. One station was chosen as a typical case for a detailed introduction as there is a large number of integrated facilities in the project.

The station is 18 km away from the market town with 23 natural villages (32 villager groups), covering an area of 14.7 km² and a total population of 3860. As most of the young people in the village work outside for a long time, the elderly, women and children are permanent residents who have a good habit to save water with a small discharge of daily sewage. But during holidays, large numbers of migrant workers returning home may lead to a surge in sewage discharge. There are also problems such as unsound construction of drainage and water collection facilities, no rain and sewage diversion, and great fluctuations in water quantity and quality with seasons and weather conditions. Its domestic sewage treatment is characterized by high-standard requirements (GB18918-2002 Grade A) for treated water, and low COD of domestic sewage with an unbalanced C/N ratio.

5.3.3 Treatment Scheme

Given the large fluctuation of water inflow and high requirements for the quality of treated water on site, a multi-stage A/O biological contact oxidation sewage integrated treatment process was selected with strong resistance to impact load and outstanding treatment performance. An electrolytic dephosphorization module was added to the integrated equipment for its low efficiency in dephosphorization. The project process is shown in Fig. 5.5, with parameters of the integrated treatment equipment shown in Table 5.6. Its main structure is a lifting well with the dimension of 1000 * 2000 * 4000 mm. The specific process is presented below. First, the domestic sewage is collected into the lifting well via the household oil separating tank and septic tank. Then, suspended or precipitated super-large solid matters are separated by the grid. On this basis, sewage flows into the flow equalization tank and is pumped to the multi-stage A/O biological contact oxidation equipment by the lifting pump, and is discharged after meeting the standard. And the sludge produced by the system is transported regularly. Its operating cost is 1.4 yuan/m³ (excluding the labor cost).

Fig. 5.5

Process flow of a rural domestic sewage treatment project in Liyang, Jiangsu, China

Table 5.6 Parameters for multi-stage A/O biological contact oxidation process integrated equipment

5.3.4 Treatment Effect

The multi-stage A/O biological contact oxidation process for sewage treatment can achieve the engineering target effectively. The project equipment is stably operated with a satisfactory treatment effect. The quality of treated water can meet the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB18918-2002). The site picture is shown in Fig. 5.6.

Fig. 5.6

The site of a rural domestic sewage treatment case in Liyang, Jiangsu, China

5.3.5 Tips for Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation (especially the electrolysis dephosphorization module) and process operation.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. To ensure the normal operation of equipment, the on-site sludge should be cleaned regularly. In general, the interval for extracting sludge for delivery should be every three to six months. Besides, the sludge accumulation of the equipment should be observed regularly.

• d. The buried type equipment is adopted in this project. If the facility is submerged under extreme weather (such as heavy rain), the facility function will be restored through dredging after the normal weather.

• e. Oil pollution of the oil separation facility in the pretreatment part of the facility should be cleaned timely to ensure that oil pollution is prevented from entering the biochemical process section of the facility. In general, oil separation facilities should be cleaned once every 1–2 months.

• f. Carbon sources should be added regularly because of the low COD and unbalanced C/N ratio of the domestic sewage on-site.

• g. The rest should refer to the operation and maintenance tips of the A/O biological contact oxidation treatment process (3.4.6).

5.4 A Rural Domestic Sewage Treatment Case in Nanjing, Jiangsu, China

5.4.1 Project Overview

Features: Small-scale centralized treatment with low discharge standard for N/P

Construction time: July 2019

Construction scale: 10 m³/d

Project objective: The quality of treated water shall conform with the Level I B criteria of the Discharge standard of water pollutants for rural sewage treatment plants (DB32 3462-2020), as shown in Table 5.7.

Table 5.7 Engineering design for the quality of domestic sewage and treated water

5.4.2 Project Background

The project is located in Liuhe District, Nanjing, Jiangsu, China. As it was implemented after the issuance of the Water pollutant discharge standard for rural domestic sewage treatment plants (DB32 3462-2020), the standard described in Sect. 5.3 is no longer implemented. Pilot projects were made in 711 rural living environment improvement demonstration villages such as Shanbei Community of Xiongzhou Street and Shuangdun Community of Yeshan Street to complete the full coverage of sewage treatment plants in all-natural villages in Liuhe District, according to the “Proposals for Implementing Rural Living Environment Improvement Demonstration Village Construction of Rural Sewage Treatment plants in Liuhe District in 2019”.

This project undertakes the rural domestic sewage treatment plants in six towns and 412 stations. One site was selected as a typical case for a detailed introduction considering the extensive design scope of the project and the large number of integrated facilities. The project serves 67 households with a registered population of 218, including 144 permanent residents. Its domestic sewage treatment is characterized by relaxed requirements for TN and TP treatment, high requirements for removal of ammonia nitrogen, and low COD of domestic sewage with an unbalanced C/N ratio.

5.4.3 Treatment Scheme

Given the large fluctuation of water inflow and low requirements for the treatment of TN, a SND biological contact oxidation integrated sewage treatment process was selected with strong resistance to impact load and a simplified process. An electrolytic dephosphorization module was added to the integrated equipment for considering its low efficiency in dephosphorization. The process flow of the project is shown in Fig. 5.7.

Fig. 5.7

Process flow of a rural domestic sewage treatment project in Nanjing, Jiangsu, China

Parameters for the integrated treatment equipment are shown in Table 5.8. Domestic sewage collected by the pipeline flows into the equalization tank of the centralized sewage treatment station after entering the septic tank and the oil separating tank, which is then lifted by the equalization tank pump to the integrated treatment equipment for treating and is discharged after meeting the standard. The operating cost is 1.07 yuan/m³ (excluding the labor cost).

Table 5.8 SND biological contact oxidation process integrated equipment parameters

5.4.4 Treatment Effect

Simultaneous nitrification and denitrification (SND) process adopted can achieve the project objective effectively. The integrated equipment is stably operated with a satisfactory treatment effect. The quality of treated water can meet the Level I B criteria of the Discharge standard of water pollutants for rural sewage treatment plants of Jiangsu, China (DB32 3462-2020). The site picture is shown in Fig. 5.8.

Fig. 5.8

The site of a rural domestic sewage treatment case in Liuhe district, Nanjing, China

5.4.5 Tips for Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation (especially the electrolysis dephosphorization module) and process operation.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. To ensure the normal operation of equipment, the on-site sludge should be cleaned regularly. In general, the interval for extracting sludge for delivery should be every 3 to 6 months. Besides, the sludge accumulation of the equipment should be observed regularly.

• d. The buried equipment is adopted in this project. If the facility is submerged under extreme weather (such as heavy rain), the facility function will be restored through dredging after the normal weather.

• e. The rest should refer to the operation and maintenance tips of the SND biological contact oxidation process.

5.5 A Rural Domestic Sewage Discharge Standard Upgrading Project in Chongming District, Shanghai, China

5.5.1 Project Overview

Features: Tail water treatment with high requirements for treated water

Construction time: July 2021

Construction scale: 30 m³/d

Project objective: The quality of treated water shall be in conformity with the Level I A criteria of the Discharge Standard of Water Pollutants for Rural Sewage Treatment plants (DB31T 1163-2019), as shown in Table 5.9.

Table 5.9 Engineering design for the quality of domestic sewage and treated water

5.5.2 Project Background

32 rural domestic sewage treatment projects were conducted from 2017 to 2018 in Chongming District, Shanghai, China, which involves 18 towns and 234,000 households, with 17,700 treatment plants constructed. Japanese johkasou was adopted as sewage treatment equipment. The Shanghai Water Affairs Bureau found that the nitrogen and phosphorus concentration of the treated water from the johkasou failed to meet the Level I A criteria of the Discharge Standard of Pollutants of Rural Domestic sewage Treatment plants (DB31T 1163-2019) in Shanghai in a survey on the preliminary rural sewage treatment project in 2020. In response to the above problem, the whole-area upgrading and reconstruction project was proposed with a requirement that domestic sewage or johkasou treated water in areas with the condition for laying pipelines should be collected through the pressure tubes for unified treatment. For those with no condition to lay pipes, johkasou drains should be combined with the new establishment of back-end treatment plants to improve the quality of tailwater. Roughly 110,000 households are involved in the modification, and 1000 new sewage treatment plants should be built.

Construction tasks of 40 rural domestic sewage tailwater upgrading sites (with the treatment capacity of 20–120 m³/d) in three towns in Chongming District, Shanghai, China were undertaken in this project. One of the sites with a treated capacity of 30 m³/d was taken as an example. Domestic sewage of the station features: (a) NH₃–N, TN and TP failing to reach the Level I A criteria of DB31T 1163-2019; (b) low COD leading to the unbalanced C/N ratio; (c) large variations in inlet volume, that is, the inflow volume is too small to reach the designed treatment capacity at normal times, whereas the inflow volume is rather large at holidays.

5.5.3 Treatment Scheme

Given the low COD concentration of water inflow and high requirements for the quality of treated water, a multi-stage A/O biological contact oxidation sewage integrated treatment process was selected with strong resistance to impact load, outstanding treatment performance, and less input of carbon sources. An electrolytic dephosphorization module was added to the integrated equipment considering its low efficiency in dephosphorization. The project process flow is shown in Fig. 5.9. Parameters for the integrated processing equipment are shown in Table 5.10. The main process of sewage treatment is presented as following. Domestic sewage collected from each household first flows into the johkasou for treatment after entering the septic tank, with the treated tail water collected through the lifting well. Then, sewage enters the equalization tank in a centralized manner under pump power. After that, it is lifted into the integrated treatment equipment for end treatment by the pump in the equalization tank, which is finally discharged up to the standard. The operating cost is 0.78 yuan/m³ (excluding the labor cost).

Fig. 5.9

Process flow of a rural domestic sewage discharge standard upgrading project in Chongming, Shanghai, China

Table 5.10 Multi-stage A/O biological contact oxidation process integrated equipment parameters

5.5.4 Treatment Effect

The multi-stage A/O biological contact oxidation process can achieve the engineering target effectively. The integrated treatment equipment is stably operated with a satisfactory treatment effect. The quality of treated water can be in conformity with the Level I B criteria of the Discharge Standard of Water Pollutants for Rural Sewage Treatment plants of Shanghai, China (DB31T 1163-2019). The site picture is shown in Fig. 5.10.

Fig. 5.10

The site of a rural domestic sewage discharge standard upgrading case in Chongming District, Shanghai, China

5.6 Tips for Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation (especially the electrolysis dephosphorization module) and process operation.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. Carbon sources should be supplemented to get the TN of treated water under control. The supplementary amount of carbon source is determined by the C/N ratio of domestic sewage and the actual removal efficiency of TN.

• d. Process operation parameters can be flexibly controlled according to the seasonal characteristics of the quality of tail water from the johkasou. If the quality of tail water is good in summer, the aeration volume of the aerobic zone and the reflux ratio of nitrifying liquid can be appropriately lower to achieve energy saving and carbon reduction.

• e. To ensure the normal operation of equipment, the on-site sludge should be cleaned regularly. In general, the interval for extracting sludge for delivery is done every 3 to 6 months. Besides, the sludge accumulation of the equipment should be observed regularly.

• f. The cleaning of sundries such as leaves, and branches should be highlighted during maintenance since the equipment station is set up in the forest. It is aimed at preventing these sundries from falling into the equipment, thereby affecting the treatment effect of the equipment.

• g. The rest refers to the operation and maintenance points of the multi-stage A/O biological contact oxidation process (3.4.6).

5.7 A Rural Domestic Sewage Treatment Case in Huangshan, Anhui, China

5.7.1 Project Overview

Features: Centralized Treatment in Large Scale

Construction Time: September 2019

Construction Scale: 200 m³/d

Project objective: The quality of treated water shall be in conformity with the first level B criteria of the Discharge Standard of pollutants for Municipal Sewage Treatment Plants (GB 18918-2002), as shown in Table 5.11.

Table 5.11 Engineering design for the quality of domestic sewage and treated water

5.7.2 Project Background

The Huangshan Municipal People’s Government decided to implement the PPP project of rural sewage treatment to improve the rural sewage treatment capacity, guarantee the quality of the water environment, and ensure the safety of drinking water in the downstream areas and the Yangtze River Delta region. The PPP project is expected to operate for 15 years with a total investment of 450,000,000 yuan, and 70 plant stations were built with a treatment capacity of 8000 m³/d. This project is part of the PPP phase 1 project for rural sewage treatment in Huangshan, Anhui, China, which serves 1 village with 595 households covering 2055 people, including 1678 permanent residents. Domestic sewage discharge is characterized by:

(a) Residents living in a concentrated area are convenient for the centralized collection and treatment of domestic sewage; (b) the standard of treated water is lax.

5.7.3 Treatment Scheme

Given the lax standard for water treatment of the project and the adoption of a large-scale centralized treatment mode, the A³/O-MBBR (mud-film composite) integrated sewage treatment process with small floor space, and stable and low energy consumption is selected in this project. The process flow is shown in Fig. 5.11, with parameters of the integrated processing equipment shown in Table 5.12. The main process is presented below: domestic sewage collected by the pipeline flows into the equalization tank by gravity for homogeneous and equalized treatment after large, suspended solids are removed by the screen. Then, the sewage is pumped into the A³/O-MBBR (mud-film composite) integrated sewage treatment equipment and is discharged after reaching the standard. And the excess sludge is discharged into the sludge thickening tank before delivering out for landfill or composting. The integrated equipment for sewage treatment is installed on the ground. The construction cost of the project is 5,000 yuan/m³, and the operating cost is 0.7 yuan/m³ (excluding the labor cost).

Fig. 5.11

Process flow of a rural domestic sewage treatment project in Huangshan, Anhui, China

Table 5.12 Parameters for A³/O-MBBR process integrated equipment

5.7.4 Treatment Effect

A³/O-MBBR integrated sewage treatment process can achieve the project objective effectively. The integrated treatment equipment is operated in good condition. The quality of treated water is in conformity with the first level B criteria of the “Pollutant discharge standard for municipal sewage treatment plants” (GB 18918-2002). The site picture is shown in Fig. 5.12.

Fig. 5.12

The site of a rural domestic sewage treatment case in Huangshan, Anhui, China

5.7.5 Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation and process operation.

• b. A daily water quality monitoring system is established to regularly monitor the water quality of domestic sewage and treated water.

• c. Daily sludge discharge of the equipment is reasonably adjusted according to the water quality and quantity.

• d. The rest refer to the operation and maintenance points of the A³/O-MBBR process (3.1.6)

5.8 A Domestic Sewage Treatment Case in Chongqing Yangtze River Protection Rural Scenic Spots

5.8.1 Project Overview

Features: Centralized Treatment in Large Scale

Construction Time: June 2021

Construction Scale: 250 m³/d

Project objective: The quality of treated water shall be in conformity with the first level of the Discharge standard of water pollutants for rural sewage treatment plants (GB 18918-2018), as shown in Table 5.13.

Table 5.13 Engineering design for the quality of domestic sewage and treated water

5.8.2 Project Background

As the Yangtze River is the mother river of the Chinese nation, its ecological protection and restoration are highly concerned with sustainable economic and social development. The Yangtze River Protection Law of the People’s Republic of China came into force on 1st March 2021. And Chongqing plays an irreplaceable role in the ecological security of the middle and lower reaches of the Yangtze River as the last pass of the ecological barrier in the upper reaches. 16 new sewage treatment stations in Jiangjin District and 11 new sewage treatment stations in Liangping District are involved in the Chongqing Yangtze River Protection Sewage Treatment Project, covering integrated equipment with treatment capacities of 20 m³/d (2 sets), 30 m³/d (1 set), 40 m³/d (3 sets), 50 m³/d (28 sets), 60 m³/d (2 sets), 75 m³/d (8 sets), 120m³/d (4 sets), 125 m³/d (2 sets) set), and 150 m³/d (2 sets) in total. One of the stations covering 120 m³/d is undertaken in this project. The sewage at this site is from the scenic spot, featuring that (a) There are tourist distribution points such as farmhouses and summer resorts in the scenic spot. (b) The complete sewage pipe network in the scenic spot can collect sewage easily. In this way, sewage can be treated in a large centralized mode. (c) Sewage volume varies widely in different seasons. In winter, there is a small sewage volume for there are only permanent residents in the scenic spot. But there are many tourists in summer with 400–800 tourists per day. The water consumption increases together with the rising sewage discharge.

5.8.3 Treatment Scheme

The multi-stage A/O contact oxidation process with a strong resistance to impact load is adopted considering that the scenic spot where the project is located has a great difference in water quality and quantity. The process flow is shown in Fig. 5.13, with parameters of the integrated processing equipment shown in Table 5.14. The domestic sewage flows into the equalization tank through the screen and is discharged up to the standard after being treated by the multi-stage A/O biological contact oxidation integrated treatment equipment. The integrated equipment for sewage treatment is installed on the ground, with the operating cost of 1.1 yuan/m³ (Excluding the labor cost).

Fig. 5.13

Process flow of a sewage treatment case of Yangtze River protection in Chongqing, China

Table 5.14 Parameters for multi-stage A/O biological contact oxidation process integrated treatment equipment

5.8.4 Treatment Effect

The multi-stage A/O biological contact oxidation process for sewage treatment can achieve the engineering objective effectively. The integrated treatment equipment is operated in good condition. The quality of treated water is in conformity with the first level criteria of the “Pollutant discharge standard for rural sewage treatment plants” (DB50/848–2018).

The project site picture is shown in Fig. 5.14.

Fig. 5.14

The site of a rural domestic sewage treatment case in Chongqing Yangtze River protection spots

5.8.5 Operation and Maintenance

• a. The operation and maintenance management mode of “online monitoring and offline inspection” is adopted in daily operation and maintenance. Online monitoring is done remotely via the cloud platform, while offline regular inspections mainly include equipment operation and process operation.

• b. A daily water quality monitoring system is established to regularly monitor the water quality of domestic sewage and treated water.

• c. As seasonal differences in scenic spots are large, inspections should be strengthened during the peak tourist seasons, with operational monitoring records taken.

• d. To ensure the normal operation of equipment, the on-site sludge should be cleaned regularly. In general, the interval for extracting sludge for delivery should be every 3 to 6 months. Besides, the sludge accumulation of the equipment should be observed regularly.

• e. The rest should refer to the operation and maintenance tips of the multi-stage A/O biological contact oxidation process (3.4.6).

5.9 A Rural Domestic Sewage Treatment Case in Shiping County, Yunnan, China

5.9.1 Project Overview

Features: Decentralized + centralized, high requirements for treated water

Construction time: April 2017

Construction scale: 10 m³/d

Project objective: The quality of treated water shall be in conformity with the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB 18918-2002), as shown in Table 5.15.

Table 5.15 Reference of the quality of domestic sewage and treated water of the project (unit: mg/L)

5.9.2 Project Background

“Twelfth Five-Year Plan” for the comprehensive prevention and control of water pollution in the Yilong Lake Basin was formulated by the Shiping County, Yunnan Province in response to the “Guiding Opinions on Improving Rural Living Environment” (2014) issued by State Council. Yilong Lake, located in the southeast of Shiping County, is one of the nine plateau lakes in Yunnan. The Yilong Lake Basin is the area with the densest population in Shiping County. The irregular sewage discharge by villages in the basin significantly polluted lake water and deteriorated the aquatic ecological environment. Hence, a comprehensive environmental improvement project for villages along the Yilong Lake was planned by the government. There are two types of sewage treatment methods according to the project requirements. The first is centralized treatment, the water quality after sewage treatment reaches the Level I A standard of Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB18918-2002). The other is household treatment, the water quality upon the sewage treatment reaches Level I B criteria of GB18918-2002 (except TP).

Seventy-three centralized facilities and 887 household sewage treatment plants are constructed in this project. A³/O-MBBR process and its integrated equipment and multi-stage A/O process and its integrated equipment are utilized in centralized sewage treatment (with the treatment capacity of 10–200 m³/d). SND process and its integrated equipment are adopted in household sewage treatment (with a treatment capacity of 0.6–5 m³/d). The sewage treatment project started in 2017, and three batches of equipment supply, installation, and commissioning were implemented at the end of October 2017, 2018, and 2019 respectively.

The construction of one of the small centralized processing sites was involved in this project. It serves more than 50 farmer households, with more than 150 permanent residents. Its domestic sewage discharge is characterized by: (a) Project construction such as sewage pipelines, garbage collection rooms, public toilets, and composting tanks was completed, except for sewage treatment. (b) Sewage can be collected and treated in a centralized manner. (c) The ground installation can be selected if the temperature difference between the four seasons is small with no extreme low temperature in winter.

5.9.3 Treatment Scheme

Given the large fluctuation of water inflow and high requirements for the quality of treated water on site, a multi-stage A/O biological contact oxidation sewage integrated treatment process was selected with strong resistance to impact load and outstanding treatment performance. The process flow is shown in Fig. 5.15, with parameters of the integrated equipment shown in Table 5.16. First, the domestic sewage is collected into the lifting well via the household oil separating tank and septic tank, with suspended or precipitated super-large solid matters separated by the grid. On this basis, sewage is pumped to the multi-stage A/O biological contact oxidation integrated treatment equipment for treating and discharging after meeting the standard. And the sludge produced by the system is transported regularly. The integrated equipment for sewage treatment is installed on the ground, with an operating cost of 0.5 yuan/m³ (excluding the labor cost).

Fig. 5.15

Process flow of a rural sewage treatment case in Shiping County, Yunnan, China

Table 5.16 Parameters for multi-stage A/O biological contact oxidation process equipment

5.9.4 Treatment Effect

The multi-stage A/O biological contact oxidation process can achieve the engineering objective effectively. The project is stably operated with a satisfactory treatment effect. The quality of treated water can meet the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB18918-2002). The site picture is shown in Fig. 5.16.

Fig. 5.16

Site of a rural sewage treatment case in Shiping County, Yunnan, China

5.9.5 Tips for Operation and Maintenance

• a. Regular inspection, including equipment and process operation should be performed. Dissolved oxygen in the aerobic zone should be regularly checked to ensure it stays within a reasonable range. The domestic sewage inlet and the aeration of each aerobic functional zone should be calibrated according to the influent load.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. To ensure the normal operation of equipment, the on-site sludge should be cleaned regularly. In general, the interval for extracting sludge for delivery should be every 3 to 6 months. Besides, the sludge accumulation of the equipment should be observed regularly.

• d. The rest should refer to the operation and maintenance tips of the multi-stage A/O biological contact oxidation process (3.4.6).

5.10 A Rural Domestic Sewage Emergency Treatment Case in Dongguan, Guangdong, China

5.10.1 Project Overview

Features: Centralized and emergency treatment on large scale

Construction Time: January 2020

Construction Scale: 8000 m³/d

Project objective: The quality of treated water shall be in conformity with the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB 18918-2002), as shown in Table 5.17.

Table 5.17 Engineering design for the quality of domestic sewage and treated water

5.10.2 Project Background

There emerged problem of the amount of sewage collected in the township far exceeding the design scale of the sewage treatment plant in Dongkeng Town, Dongguan, Guangdong, China in the construction of secondary sewage interception pipeline network. Meanwhile, the existing sewage treatment plant is expanding and upgrading. Consequently, the sewage in some areas of Dongkeng Town could not be transported to the sewage treatment plant for treatment, resulting in the river being seriously polluted as well as black and odorous water. To this end, an emergency treatment project was performed. The project features (a) Large volume and high discharge standard. With the daily treatment capacity of 8000 m³, the quality of the treated water shall meet the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB 18918-2002). (b) Emergency treatment with a short construction period. The designed construction period from the design implementation to the realization of discharging after meeting the standard is only 40 days.

5.10.3 Treatment Scheme

The A/O-MBBR integrated sewage treatment process with a simple process, low investment and low operating cost was selected by the project. The technological process is shown in Fig. 5.17. The composition of the main structure of the project is shown in Table 5.18, and the equipment parameters are shown in Table 5.19. With the total designed treatment capacity of 8000 m³/d, eight sets of integrated treatment systems were connected in parallel, with each formed by three integrated treatment plants connected in series. Considering the low efficiency in phosphorus removal, the A/O-MBBR integrated sewage treatment process is equipped with a chemical phosphorus removal module (PAC). The main technological process is presented as following: Domestic sewage is discharged into the integrated lifting pump station through the collection pipe network and flows through the screen channel, the sand settling tank and the equalization tank successively. Then the influent is distributed to the integrated sewage treatment equipment by the distribution well and deeply treated via the cloth filter. Finally, the treated water is discharged or recycled after being disinfected and sterilized. The excess biochemical sludge being temporarily stored in the sludge tank is filtered by the screw press before it is transported out for disposal. The integrated equipment for sewage treatment is installed on the ground, with an operating cost of 1.01 yuan/m³ (excluding the labor cost).

Fig. 5.17

Process flow of the rural domestic sewage emergency treatment case in Dongguan, Guangdong, China

Table 5.18 Main structures of the rural domestic sewage emergency treatment case in Dongguan, Guangdong, China

Table 5.19 Parameters of A/O-MBBR integrated treatment equipment

5.10.4 Treatment Effect

The A/O-MBBR sewage treatment process can achieve the emergency treatment objective effectively. The project was completed as scheduled, with the installation done in the 5th week, and the discharge after meeting standards in the 6th week. The integrated equipment was operated stably with a satisfactory treatment effect. And all indicators of the quality of the treated water can steadily meet the discharge standard.

The site picture is shown in Fig. 5.18.

Fig. 5.18

The site of rural domestic sewage emergency treatment case in Dongguan, Guangdong, China

5.10.5 Tips for Operation and Maintenance

• a. The operation and maintenance contain eight sets of integrated treatment systems, and other auxiliary facilities supporting the same station, such as a cyclone settling tank, mechanical screen, water collection tank, lifting pump, and water distribution tank.

• b. Personnel specializing in operation, maintenance, and repair should be arranged to regularly inspect the operation of equipment and facilities and monitor the quality of domestic sewage and treated water.

• c. Sewage in zone A should be uniformly mixed to avoid local sludge accumulation. Timely dredging is needed if the mixture pipeline is found blocked.

• d. Carriers in the O zone should be checked for no accumulation, no damage, and no non-functional biological overload.

• e. The carrier block at the tail end of the O zone should be kept unobstructed.

• f. The sludge accumulated on the inclined tube carrier in the sedimentation zone should be backwashed in time.

• g. The filtration unit of the filter tank should be cleaned regularly.

• h. As fan aeration is adopted, the condition of the fan belt should be checked daily to find abnormalities such as oil leakage and abnormal noise since. Also, the filter screen of the fan air inlet must be cleaned regularly.

• i. Whether the dosing unit is normally operated should be checked regularly to avoid blockage, empty pumping, or insufficient dosage.

• j. The feeding and dosing amounts can be adjusted when abnormal dehydration is found in the screw dehydrator. Meanwhile, the blockage should be removed in time.

5.11 A Campus Domestic Sewage Treatment Case in Haikou, Hainan, China

5.11.1 Project Overview

Features: Centralized treatment on a large scale with high requirements for treated water

Construction time: December 2020

Construction scale: 1500 m³/d

Project objective: The quality of treated water shall be in conformity with the Level I A criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB 18918-2002), as shown in Table 5.20.

Table 5.20 Engineering design for the quality of domestic sewage and treated water

5.11.2 Project Background

According to the “13th Five-Year Plan for the Construction of Urban Sewage Treatment plants in Hainan” issued by the Hainan Provincial Development and Reform Commission and the Provincial Department of Water Affairs in 2017, the comprehensive treatment capacity of urban sewage should be further improved to reach a centralized sewage treatment rate of more than 85% in the cities, counties and towns in Hainan province.

The project, located in Haikou, Hainan, involves the treatment of domestic sewage on a new campus. The sewage pipe network around the campus is not completed, and the domestic sewage generated on campus cannot be discharged to the sewage treatment plant. Hence, supporting sewage treatment plants are needed.

There are approximately 7000 faculties and students in the new school according to a field survey and data provided by school officials. The comprehensive domestic water consumption standard is determined as 200L/(person·d) with reference to the per capita comprehensive water consumption index of Haikou, Hainan, China, based on the current situation of school water consumption and long-term planning. And the design scale of the sewage treatment station on campus is 1500 m³/d based on the forecast of comprehensive water consumption and the construction of the sewage treatment station. Treated water shall meet the Level I A criteria of the Discharge Standard of Pollutants for Municipal Sewage Treatment Plants (GB 18918-2002).

5.11.3 Treatment Scheme

To meet the requirement of treated water quality, the A³/O-MBBR (mud-film composite) integrated sewage treatment process with satisfactory denitrification and phosphorus removal was selected. The process flow is shown in Fig. 5.19. The composition of the main structure of the project is shown in Table 5.21 Parameters of the integrated treatment device are shown in Table 5.22 The total sewage treatment capacity is 1500 m³/d, which is realized in the parallel operation of the A³/O-MBBR integrated sewage treatment equipment with a daily treatment capacity of 250 m³. The project was developed in two phases, and the case selected undertook the construction of the first phase with a design water volume of 750 m³/d, which involved three integrated facilities.

Fig. 5.19

Process flow of a domestic sewage treatment case on campus in Haikou, Hainan, Chi

Table 5.21 List of main structures

Table 5.22 Parameters for A³/O-MBBR process equipment

The main process flow is as follows: Domestic sewage collected by the pipeline flows into the equalization tank by gravity for homogeneous and equalized treatment after large suspended solids are removed by the screen. Then, the sewage is pumped into the Beisi efficient biological reactor. Treated water is sterilized and discharged after meeting the standards. And the excess sludge is discharged into the sludge thickening tank before transportation for landfill or composting. The integrated equipment for sewage treatment is installed on the ground in this project. The construction cost is 8500 yuan/m³, with an operating cost of 0.7 yuan/m³ (excluding the labor cost).

5.11.4 Treatment Effect

The A³/O-MBBR process can achieve the project objective effectively. The phase 1 project with a treatment capacity of 750 m³/d was put into operation, and the integrated equipment is stably operated with a satisfactory treatment effect. The quality of treated water can meet the Level I A Criteria of the Pollutant Discharge Standard of Water for Municipal sewage treatment plants (GB18918-2002). The site picture is shown in Fig. 5.20.

Fig. 5.20

Site of A domestic sewage treatment case on campus in Haikou, Hainan, China

5.11.5 Tips for Operation and Maintenance

• a. One person specializing in operation and maintenance should be arranged to regularly inspect the operation of equipment and process.

• b. A daily water quality monitoring system should be established to regularly monitor the water quality of domestic sewage and treated water.

• c. Sludge discharge of the equipment should be reasonably adjusted according to the water quality and quantity, so as to maintain the concentration stability of the sludge in the system.

• d. Given the periodicity of domestic sewage discharge on campus, sludge discharge of all facilities is closed before the summer and winter holidays. Meanwhile, three air pumps of the parallel equipment are kept in intermittent operation during holidays to reduce the degradation of sludge in the lack of organic matters from domestic sewage, and industrial glucose should be regularly dosed in preparation for the smooth startup of equipment after the holidays.

• e. The rest should refer to the operation and maintenance tips of the A³/O-MBBR (Integrated fixed-biofilm activated sludge) process.