Diagnosing and Characterizing the Mechanisms of Biological Phosphorus Removal at the Great Lakes Water Authority (GLWA) Water Resource Recovery Facility (WRRF)

Previous research has demonstrated that biological phosphorus removal (bio-P) occurs in the Great Lakes Water Authority (GLWA) Water Resource Recovery Facility (WRRF) High Purity Oxygen Activated Sludge (HPO-AS) process, suggesting that sludge fermentation in the secondary clarifier sludge blanket is key to bio-P occurrence. This study, combining batch reactor testing, the development of a process model for the HPO-AS process using Sumo21 (Dynamita), and the analysis of eight and a half years of plant operating data, showed that bio-P consistently occurs at the GLWA WRRF. This occurrence is attributed to the unique configuration of the HPO-AS process, which has a relatively large secondary clarifier compared to the bioreactor, and the characteristics of the influent wastewater, primarily particulate matter with limited concentrations of dissolved biodegradable organic matter. The volatile fatty acids (VFAs) needed for polyphosphate accumulating organisms (PAOs) growth are produced in the secondary clarifier sludge blanket, which provides more than four times the anaerobic biomass inventory compared to the anaerobic zones in the bioreactor, thus facilitating bio-P in the current system. Opportunities exist to further optimize the phosphorus removal performance of the HPO-AS process and reduce the amount of ferric chloride used. These findings may be of interest to researchers investigating biological phosphorus removal in similar systems.