Tennessee Wastewater Operator Practice Exam

What term describes the material entering the digester?

1. Effluent

2. Feed sludge

3. Return activated sludge

4. Sludge blanket

The correct answer is: Feed sludge

The material entering the digester is referred to as feed sludge. This terminology is widely used in wastewater treatment to indicate the organic and inorganic solids that are delivered to the digester, where anaerobic digestion occurs. During this process, microorganisms break down the feed sludge, leading to the reduction of volatile solids and the production of biogas, which can be captured for energy use. Understanding this term is important because it relates directly to the operational processes within a wastewater treatment plant, particularly in the anaerobic digestion phase. The proper management of feed sludge is crucial for optimizing digestion efficiency, maintaining balanced microbial populations, and ensuring the effective removal of waste products from the system. In contrast, the other terms refer to different aspects of wastewater treatment; for instance, effluent is the treated water that exits the treatment process, return activated sludge is recycled sludge returned to the aeration tank to help maintain microbial populations, and sludge blanket refers to the layer of accumulated solids present in certain processes, such as in secondary clarifiers. Each of these plays a different role within the system and is not specifically the material entering the digester.