Final answer:
A trickling filter is a secondary filter in a wastewater treatment process that reduces organic load through a combination of biological and physical techniques. It precedes additional purification steps such as aeration, clarification, and tertiary treatment, which includes advanced filtration and nutrient removal.
Step-by-step explanation:
A trickling filter can be used as a secondary filter to reduce the organic load of the wastewater prior to another biological process. The trickling filter is a type of filtration system that involves biological treatment as well as physical separation. In this process, wastewater is spread over a bed of media such as rocks, gravel, or specially designed plastic media that provide a surface for microbial growth. As the wastewater trickles over the media, the microorganisms consume the organic material, effectively reducing the organic load of the wastewater.
Following the trickling filter, the treated water can undergo further purification, such as secondary aeration and clarification, where oxygen is introduced to support aerobic digestion of remaining contaminants. Subsequently, the water might pass through sedimentation tanks and be subjected to additional filtration, like sand filtration or charcoal carbon filters, to remove any residual particulates, reduce turbidity and odors, and decrease the iron content. This multistage treatment ensures the wastewater is adequately cleaned before final discharge or reuse.
Tertiary treatment, also known as effluent polishing, is an example of a subsequent biological process that may follow a trickling filter, especially when the effluent is being released into a sensitive ecosystem. This stage aims to further reduce nutrients such as nitrogen and phosphorus and includes methods like enhanced biological phosphorus removal, which utilizes specific bacteria to eliminate excess phosphorus from the wastewater.