Engineering concerns and new developments in anaerobic waste-water treatment

Abstract

A non-comprehensive review of several developments in the field of anaerobic biological waste-water treatment engineering is carried out, considering the active role engineers have to play in this field. The analysis is done as a result of the fact that the general performance of anaerobic systems and the diversity of wastes that these can treat are increasing as a result of new reactor design, operating conditions, and use of specialized microorganisms. This paper illustrates a few examples of conventional and new applications of anaerobic treatment and several advantages, such as no energy-intensive oxygen transfer, less excess sludge, production of combustible biogas, and space saving. Such an overview of biological waste-water treatment also precedes comments on some important aspects on process microbiology as well as considerations of the application of fundamentals and kinetics to the analysis of the biological processes used most commonly for anaerobic biological waste-water treatment.

Models developed for this reaction type are discussed, considering four overall steps. Also, models for a continuous-stirred tank bioreactor, a fluidized bed reactor, and a packed bed reactor as basic configurations are described.

Major anaerobic biological treatment processes used for waste-water treatment, both suspended-growth processes and reactors (anaerobic stirred tank, anaerobic contact process, upflow anaerobic sludge-blanket process) and attached-growth processes and reactors (anaerobic filter process, expanded-bed process), are considered. It was also shown that the breakthroughs dealing with reactor design and operating conditions offer practical solutions to many of the drawbacks that were initially thought to limit the purpose of anaerobic processes.

Finally, the paper includes some aspects regarding the control of anaerobic biological systems.