EBPR with Struvite Recovery to Reduce Chemical Consumption and Increase Nutrient Removal Reliability

Two alternatives were investigated for reducing chemical addition at a water reclamation facility with regional anaerobic digestion recycle streams: 1. the MLE process with alum addition for P removal and denitrifying filters for N removal (MLE alternative), and 2. the 5-stage Bardenpho alternative process for enhanced biological phosphorus removal, activated sludge biological denitrification using methanol addition and the Ostara struvite-recovery recycles treatment process. The 5-stage Bardenpho alternative resulted in annual cost operational savings of 640,000–800,000 compared to MLE alternative, a 13- to 18-year payback period, reduced chemical and electrical energy consumption, and increased net digester methane gas production. Process performance would significantly increase: the 14 percent reduction in future average MLSS concentration would reduce the secondary clarifiers load and increase process stability; the effluent total phosphorus concentration and the nitrate load of the denitrifying filters would be approximately halved, leading to enhanced nutrient removal treatment and reliability.