Tennessee Wastewater Operator Practice Exam

Which test provides the best measure of microorganisms in the activated sludge process?

1. MLVSS

2. BOD

3. COD

4. D.O. measurement

The correct answer is: MLVSS

The best measure of microorganisms in the activated sludge process is the MLVSS, which stands for Mixed Liquor Volatile Suspended Solids. This test quantifies the amount of volatile suspended solids present in the mixed liquor of an activated sludge system, which includes bacteria and other microorganisms that are essential for the biological treatment of wastewater. The MLVSS value is particularly significant because it differentiates between organic materials that can decompose (the microorganisms) and inorganic materials present in the suspended solids. Therefore, a higher MLVSS concentration indicates a greater quantity of microbial biomass available to facilitate the treatment processes. This biochemical activity is crucial for effectively breaking down organic matter in the wastewater. Understanding MLVSS provides operators with insight into the health and activity level of the microbial population. It informs adjustments needed in aeration, waste removal, and other operational parameters to optimize treatment efficiency. While BOD (Biochemical Oxygen Demand) measures the amount of oxygen required by microorganisms to decompose organic matter, it does not specifically quantify the microorganisms themselves. COD (Chemical Oxygen Demand) assesses the total oxygen demand of all oxidizable substances in water, not just the biodegradable portion. D.O. (Dissolved Oxygen) measurement reflects the amount of oxygen available to aquatic life