Tennessee Wastewater Operator Practice Exam

What does a high BOD loading in a secondary treatment plant typically lead to?

1. Improved nutrient recycling

2. Enhanced pathogen removal

3. Increased operational costs

4. Lower sludge production

The correct answer is: Increased operational costs

A high biochemical oxygen demand (BOD) loading in a secondary treatment plant indicates that the wastewater has a significant amount of organic material that microorganisms will need to decompose. This increased demand can lead to several challenges for the treatment plant. When BOD levels are high, the microbial population becomes more active and requires more oxygen to break down the organic matter. This can necessitate increased energy inputs for aeration, leading to higher operational costs, as more air is supplied to maintain sufficient oxygen levels for microbial metabolism. Additionally, staff may need to manage and monitor the system more intensively, contributing further to operational costs. While high BOD can sometimes improve nutrient recycling or affect pathogen removal indirectly, these options do not capture the immediate economic ramifications associated with managing higher organic loads. Likewise, higher BOD typically results in increased sludge production rather than lower sludge production, as the breakdown of organic material generates additional biomass. Thus, understanding the costs associated with energy and operational demands is key to managing a secondary treatment plant effectively.