Wastewater Treatment Operator Certification Practice Test

What are screenings in wastewater treatment?

1. Colloids

2. Total Dissolved Solids (TDS)

3. Pieces of wood, roots, rags, and other large debris

4. Chemical Oxygen Demand (COD)

The correct answer is: Pieces of wood, roots, rags, and other large debris

Screenings in wastewater treatment refer specifically to materials that are collected from the influent flow to prevent large debris from entering further stages of treatment. These materials often include pieces of wood, roots, rags, and other large debris that can cause clogs or damage to equipment downstream. Screenings are typically removed during the preliminary treatment phase, which is designed to protect the more sensitive and intricate treatment processes that follow. The purpose of removing these large items is multifaceted: it helps to maintain operational efficiency, reduces maintenance costs, and protects the integrity of the treatment plant. Effective screening is crucial because it ensures smoother operation of pumps and clarifiers while also preventing unwanted materials from interfering with biological treatment processes. In contrast, options like colloids, Total Dissolved Solids (TDS), and Chemical Oxygen Demand (COD) refer to more technical aspects of water quality and contaminant measurement and do not relate directly to the physical debris managed through screening processes. Colloids are fine particles that remain dispersed in water, TDS represents the soluble portion of pollutants, and COD is a measurement of the organic content in water. These factors are important in wastewater treatment but do not describe screenings specifically.