Detection and prevention of enhanced biological phosphorus removal deterioration caused by Zoogloea overabundance

A sequencing batch reactor was operated in the conventional anaerobic-aerobic mode for enhanced biological phosphorus removal using acetate as the sole substrate. Despite the nutrients concentrations in the influent being high enough to satisfy the biological requirements, Zoogloea ramigera managed to grow in the system until it had negative effects on the process performance. The excess of exocellular polymeric material produced by this microorganism contributed to a viscous bulking phenomenon and caused important settling problems. The examination of the sludge under the microscope was a valuable tool to diagnose the cause of the imbalance in the process. The strategy adopted to avoid the deterioration of the process (changing key operational factors affecting the Z. ramigera development) allowed the successful recovery the enhanced biological phosphorus removal system. The effectiveness of this approach was confirmed by analyzing several parameters along the operational period (SVI, Y(PO4), TSS, %VSS...) together with microbiological examinations of the sludge.