Tennessee Wastewater Operator Practice Exam

What is the outcome if the organic loading rate to the first stage of treatment in an RBC is excessively high?

1. Oxygen contraction will increase

2. Oxygen contraction will decrease

3. Effluent quality will improve

4. Sludge production will drop

The correct answer is: Oxygen contraction will decrease

When the organic loading rate to the first stage of treatment in a Rotating Biological Contactor (RBC) is excessively high, the system can become overloaded with organic material. This can lead to a situation where the microorganisms present in the system are unable to adequately process the organic matter due to the sheer volume. As a result, the respiration rate of the bacteria may increase, consuming more oxygen than what is available in the system to maintain efficient biological treatment. Consequently, this can lead to a decrease in the overall oxygen concentration within the RBC because the aeration might not be sufficient to support the heightened demand for oxygen from the microorganisms. A decrease in oxygen levels can impair the aerobic treatment process, leading to suboptimal degradation of organic materials and potentially resulting in increased concentrations of pollutants in the effluent. Maintaining an appropriate organic loading rate is critical for the effective functioning of the RBC, as it ensures that microorganisms have enough oxygen to efficiently break down organic substances without overwhelming the system. In contrast, a controlled and balanced loading rate allows for optimal oxygen levels, enhancing treatment efficacy and improving the quality of the effluent produced.