Challenges to Achieving Stable Performance in a Site-Specific EBPR Configuration (AAnO) at the Stickney Water Reclamation Plant

After a site-specific enhanced biological phosphorus removal (EBPR) configuration was developed without major infrastructural change to the existing secondary treatment facility, the entire Stickney Water Reclamation Plant (WRP) was converted to this configuration in fall 2013. This site-specific EBPR configuration consists of anoxic, anaerobic, and oxic zones (AAnO) in sequence. Since the conversion, the plant treatment efficiency with respect to effluent BOD5, suspended solids, and ammonia nitrogen has not been noticeably affected, while the effluent total phosphorus concentrations are lower. However, the EBPR performance has not reached the desired level. Occasional occurrences of the elevated dissolved oxygen (DO) and nitrate levels in the return activated sludge (RAS), shortage of carbon in the influent, and elevated chloride concentrations in the winter months pose operational challenges to this process. The potential strategies in addressing these challenges will be discussed here.