Troubleshooting Activated Sludge Performance through Microscopic Observations: Five Case Studies

Plant operators rely on many tools to observe and evaluate the Wastewater Treatment Plant (WWTP) process. For example, a laboratory analysis showing increasing effluent ammonia may lead an operator to increase the aerobic volume used in treatment. Or a hand-held Dissolved Oxygen (DO) meter showing low DO concentrations may inform an operator to increase the aeration output to the aeration tanks (ATs).Another valuable tool for operational staff is microscopic analysis of the activated sludge. Routine microscopic analysis allows a continuous database of the “health” of the activated sludge to be determined and acts as an early warning of any potential settling (bulking) and/or foaming problems.Filamentous bulking is due to the dominance of filamentous organisms, which interfere with the settling properties of the activated sludge. Activated sludge foaming is often caused by the presence of filamentous bacteria, like Nocardioforms, which are hydrophobic in nature and interact with gas bubbles, promoting free-form filament attachment to these bubbles in the bulk solution, which rise to the surface as foam.Five case studies are presented, demonstrating examples where microscopic analysis provided identification of filamentous microorganism populations and associated corrective action.