Tennessee Wastewater Operator Practice Exam

Maintaining a constant MLSS concentration approximates a constant SRT when what condition is met?

1. Influent BOD and TSS loads are nearly constant

2. The plant operates at peak efficiency

3. Bacteria population is consistently monitored

4. Temperature variations are minimal

The correct answer is: Influent BOD and TSS loads are nearly constant

Maintaining a constant Mixed Liquor Suspended Solids (MLSS) concentration is crucial for ensuring a consistent Solids Retention Time (SRT) in a wastewater treatment system. When the influent Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) loads are nearly constant, it allows for a more predictable and stable environment for the microbial population within the treatment process. A consistent influent BOD ensures that the microorganisms have a stable food source to break down, promoting a healthy growth rate and maintaining a balance in the biomass. The TSS load, which indicates the amount of solids entering the treatment system, also plays a vital role. With stable influent loads, the treatment plant can effectively manage the solids by controlling the amount of biomass that is wasted, thereby achieving a steady-state condition where MLSS remains constant and SRT is maintained. In contrast, other factors such as plant efficiency, monitoring of bacteria populations, and temperature variations can impact the treatment process but do not directly correlate with maintaining both a stable MLSS and SRT. Plant inefficiencies might lead to inconsistent MLSS levels, while fluctuating bacteria populations can alter the treatment dynamics. Temperature variations could affect microbial activity and settling characteristics. Thus,