Why is it important to maintain adequate return sludge flow to the aeration basin?

• A. To Increase Chemical Dosing
• B. To Preserve Biomass, Maintain MLSS And SRT, And Ensure Stable Treatment Performance
• C. To Prevent Foaming
• D. To Reduce Temperature of the Aeration Basin

Answer: (B)

Returning activated sludge to the aeration basin keeps the biological mass in the reactor at the necessary level. By recycling settled solids, you maintain the right mixed liquor suspended solids (MLSS) and keep the solids retention time (SRT) long enough for the microbial population, including slower-growing organisms, to stay active. This ensures there are enough microbes to consistently metabolize organics, maintain stable treatment performance, and produce a reliable effluent. If the return flow is too low, solids are carried out with the effluent, MLSS drops, SRT shortens, and treatment can become unstable with poorer removal and more variable results. While other factors can influence foaming or temperature, they are not the primary purpose of maintaining adequate return sludge flow.