Biological Treatment Techniques for Sewage: Aerobic and Anaerobic Processes

Abstract

Sewage treatment is crucial to safeguard public health and the environment. Various techniques are available for treating wastewater, and the selection of one often depends on factors like the wastewater composition, environmental conditions, and treatment objectives. One of the most widely used methods of biological treatment for sewage is activated sludge, which employs aerobic bacteria to degrade organic matter. This process involves blending wastewater with a mixture of bacteria and flocs, with the bacteria consuming the organic matter to produce clear water while the flocs settle. Another commonly employed method is anaerobic digestion, which employs anaerobic bacteria to decompose organic matter in the absence of oxygen. These methods generate biogas, containing methane and carbon dioxide, and digestate, a nutrient-rich sludge suitable as soil amendment or fertilizer. This chapter explores the mechanisms and applications of activated sludge and anaerobic digestion in biological sewage treatment, highlighting their advantages and downsides, the factors that influence their performance, such as pH, temperature, and substrate concentration. It covers the latest improvements in biological sewage treatment, including the use of new microbial strains and hybrid treatment systems.