Wastewater New York State Practice Exam Prep & Practice Tests

An increase in primary effluent solids when influent total solids are normal can be attributed to decreased detention time. Detention time refers to the length of time that wastewater is held in a treatment tank. When the detention time is decreased, there is less opportunity for solids to settle out of the water. This can result in a higher concentration of suspended solids in the primary effluent because the solids are not given enough time to be effectively removed from the wastewater before it leaves the treatment system.

In typical wastewater treatment processes, adequate detention time is crucial for effective sedimentation, which is the process that allows solids to settle to the bottom of a tank. If the retention time is shortened, the system may not operate efficiently, leading to increased levels of solids in the effluent, even when the influent total solids remain normal.

While excessive aeration, increased flow rate, and impaired sludge digestion can impact overall treatment performance, these factors do not directly correlate with an increase in primary effluent solids under normal influent conditions as clearly as decreased detention time does.