What process follows the biological breakdown of organic matter in sewage treatment?

The correct answer pertains to the sequence of processes involved in sewage treatment, particularly after the biological breakdown of organic matter has occurred. Following this breakdown, the primary objective is to further purify the effluent and remove residual solids, pathogens, and contaminants from the treated sewage.

Filtration is a critical step in this sequence, as it involves the physical removal of remaining suspended particles and microorganisms. Through filters or membranes, clarified effluent is polished after biological treatment—ensuring cleaner water is discharged or reused.

Chlorination, while important for disinfection, typically occurs as a subsequent step after filtration to eliminate any remaining pathogens. Similarly, coagulation, which is primarily used to aggregate suspended particles and facilitate their removal, is also not performed directly following biological treatment but rather in earlier stages to help in solids removal.

Understanding these steps in the context of sewage treatment processes is crucial because they illustrate how different methods are integrated to achieve effective sanitation, thereby protecting public health and the environment. Hence, among the provided options, filtration directly follows biological breakdown as a step in the overall treatment process.