What is one of the major goals of secondary treatment in wastewater treatment?

One of the major goals of secondary treatment in wastewater treatment is to enhance the microbial removal of organic matter. This stage is crucial because it focuses on reducing the biological load of the wastewater. Secondary treatment often employs microorganisms to decompose organic pollutants. These microbes break down remaining organic substances that were not removed during the primary treatment phase, significantly improving the quality of the effluent.

In this process, aeration tanks or biological reactors may be used, where oxygen is supplied to foster the growth of bacteria that feed on the organic material in the wastewater. The result is a significant reduction in biochemical oxygen demand (BOD) and total suspended solids (TSS), leading to cleaner water that is safer to discharge into the environment or to undergo further treatment.

The other options relate to different aspects of wastewater treatment. The removal of grit and sand pertains to primary treatment, where heavier solids are settled out. Chemical disinfection typically occurs after secondary treatment to eliminate pathogens. Dewatering of solids is a process associated with solids handling and treatment rather than the core objective of secondary treatment itself. Thus, the focus of secondary treatment on enhancing microbial action for organic matter removal makes it a vital step in achieving effective wastewater treatment.