Which methods are commonly used in secondary treatment?

Secondary treatment methods are focused on the biological processes that remove dissolved and suspended organic matter from wastewater. Trickling filters and biofilm reactors are well-established techniques that emphasize the role of microbes in breaking down pollutants.

Trickling filters utilize a fixed bed of media, often made of rocks or plastic, over which wastewater is spread. As the wastewater trickles down through the media, biofilms, composed of microorganisms, grow on the surfaces and degrade organic material. This process enhances the removal of BOD (biochemical oxygen demand) and other organic compounds.

Biofilm reactors, similar in principle, provide a space where microorganisms can attach and form a biofilm, allowing efficient treatment as the wastewater flows through. This method excels in nutrient removal and enhances the overall treatment efficiency.

In contrast, methods such as chlorination and filtration generally pertain more towards disinfection and final effluent polishing rather than the primary biological treatment of organic pollutants. Precipitation and evaporation are not typical methods of secondary treatment but rather pertain to other stages in the treatment process, focusing on the physical removal of solids or concentration. Hence, the use of trickling filters and biofilm reactors is central to secondary treatment, highlighting the biological approach that is characteristic of this stage in wastewater treatment