Wastewater Treatment Operator Certification Practice Test

What is the slime growth on a trickling filter called?

1. Filamentous bacteria

2. Zoogleal film

3. Stalked ciliate

4. Acid formers

The correct answer is: Zoogleal film

The slime growth on a trickling filter is referred to as the zoogleal film. This term describes the slimy layer that develops on the surface of the filter media, which consists primarily of microbial communities, including bacteria and protozoa. This biofilm plays a crucial role in the treatment process, as it facilitates the biological treatment of wastewater by providing a habitat where microorganisms can break down organic matter. In a trickling filter system, the wastewater is distributed over a bed of media (like rocks or plastic) where the zoogleal film can develop. As the wastewater trickles down through the media, the organic pollutants are absorbed and metabolized by the microorganisms within the biofilm. The efficiency of the trickling filter largely depends on the thickness and health of this zoogleal film, which in turn affects the overall treatment performance. Other choices, such as filamentous bacteria, stalked ciliates, and acid formers, refer to specific types of microorganisms or metabolic processes but do not specifically describe the general biofilm layer that develops in trickling filters. Each of those types has a role in wastewater treatment, but they do not collectively encompass the term used for the slime growth in this particular context.