What is the primary function of a trickling filter?

The primary function of a trickling filter is the removal of soluble biochemical oxygen demand (BOD) and carbonaceous biochemical oxygen demand (CBOD). Trickling filters serve as a type of biological treatment where wastewater is distributed over a bed of media (such as rocks or plastic) that supports microbial growth. This biofilm of microorganisms adheres to the media and metabolizes organic matter present in the wastewater.

As the wastewater trickles down through the media, the microorganisms consume the organic material, leading to a reduction in BOD and CBOD levels. Efficient removal of these pollutants is crucial, as it helps prevent environmental degradation and ensures that discharged water meets regulatory standards for water quality.

In contrast, other options focus on different processes not primarily associated with trickling filters. The removal of suspended solids, while sometimes aided by trickling filters, is generally more effectively accomplished by sedimentation processes. Separation of heavy metals might be more relevant to specialized treatments such as chemical precipitation or ion exchange rather than a trickling filter's biological focus. Clarification of wastewater is a separate treatment step often handled in settling tanks or clarifiers, which sediment suspended solids rather than biological breakdown.