How does secondary treatment differ from primary treatment?

Secondary treatment is fundamentally characterized by the biological degradation of organic matter in wastewater. Unlike primary treatment, which primarily focuses on the physical removal of larger solids and sedimentation processes, secondary treatment employs microbial processes to further break down dissolved and suspended organic materials.

This biological process typically involves the use of microorganisms (such as bacteria) that consume organic matter, converting it into biomass and gases. This treatment can occur in various forms, such as activated sludge systems or trickling filters, emphasizing the significant role of microorganisms in treating wastewater to produce cleaner effluent.

In contrast, other options do not accurately represent the functional focus of secondary treatment. While chemical processes are essential in some contexts of wastewater treatment, they do not define secondary treatment, and the removal of large solids is a primary treatment function, not a secondary one. Lastly, secondary treatment is not necessarily the last step before effluent discharge; additional treatments may follow to ensure compliance with environmental regulations and standards. Therefore, the emphasis on biological degradation distinctly defines secondary treatment.