A Small Footprint Approach for Enhanced Biological Phosphorus Removal: Results from a 106 mgd Full-scale Demonstration

Enhanced biological phosphorus removal (EBPR) has become a widespread and effective method for reducing effluent phosphorus at municipal activated sludge wastewater treatment facilities. Often times, a conventional design approach for EBPR is feasible. However, already existing site-constrained large-scale facilities faced with effluent phosphorus and nitrogen limits may find that a conventional mainstream EBPR configuration is costly and difficult to implement. An alternative sidestream EBPR approach was tested to compliment a Modified Ludzack-Ettinger (MLE) configuration integrated with a sidestream centrate and return activated sludge re-aeration basin (CaRRB) designed for compact nitrogen removal. Results from an eight-month full-scale demonstration showed excellent phosphorus removal performance. Effluent total phosphorus concentrations during the proof-of-concept phases of the demonstration averaged 0.58 mg-P/L. The design of the sidestream reactors, process modifications, results, and future design considerations are discussed.