Ace the Texas Wastewater Class B Test 2026 – Dive In and Flow to Success!

The rate of returned sludge significantly influences the growth rate of microorganisms within the biological treatment process. In wastewater treatment, returned sludge is comprised of activated sludge that is collected from the settling tank and sent back to the aeration tank. The concentration of this returned sludge directly affects the biomass present in the system. A higher return sludge rate leads to more microorganisms being available to break down organic matter, thereby increasing the efficiency of the biological treatment process. This enhancement in microbial activity is essential for effectively reducing biochemical oxygen demand (BOD) and promoting stabilizing conditions in the aeration tanks, enabling better treatment outcomes.

While other aspects such as temperature and concentration of incoming BOD are important, they are not directly influenced by the rate of returned sludge in the same manner.