Prediction of struvite formation potential in EBPR digested sludge using mass balances, batch precipitation tests, and chemical equilibrium modeling

Digested sludge liquors from wastewater treatment plants that include enhanced biological phosphorus removal (EBPR) in their treatment process have the potential to form struvite (MgNH4PO4·6H 2O). The potential can be determined by the concentrations of struvite constituents including phosphorus, ammonium, and magnesium. Phosphorus concentration of digested sludge liquors is expected to increase when EBPR is introduced to wastewater treatment plants because phosphorus accumulating organisms (PAOs) can accumulate phosphorus beyond their metabolic needs and phosphosphorus can be relased when they are digested anaerobically. The work presented in this thesis focuses on determining the potential for struvite formation at the City of Las Vegas Water Pollutant Control Facility (WPCF) due to the introduction of EBPR. Specifically, the struvite formation potential of digested sludge centrate is investigated using mass balances, batch tests, and chemical equilibrium modeling with the software MINEQL+.