What issue might cause septic wastewater to flow into the primary clarifier?

The presence of anaerobic conditions in the collection system can lead to problems such as septic wastewater flowing into the primary clarifier. Anaerobic conditions occur when there is insufficient oxygen for aerobic microbes to thrive. This can result in the breakdown of organic material by anaerobic bacteria, leading to the production of gases such as hydrogen sulfide and volatile fatty acids, which contribute to the septic state of the wastewater.

When wastewater becomes septic, it typically has a lower pH and higher levels of soluble substances that can disrupt the normal functioning of downstream treatment processes, including primary clarification. If septic conditions reach the primary clarifier, they may impede the settling of solids and affect the overall treatment efficiency of the facility.

The other options, while they may relate to the functioning of the wastewater system, do not directly cause septic wastewater to enter the primary clarifier in the same way that anaerobic conditions do. For example, aerobic conditions in the collection system promote the breakdown of organic material by aerobic bacteria, which typically results in more stable and less problematic wastewater. Lift station pumps operating on short cycles can cause fluctuations in flow but do not inherently create septic conditions. Finally, high flows due to low Mean Cell Residence Time (MCRT) may indicate excessive flushing of the system