Effective Use of Process Modeling for a Comparison of Sludge Dewatering Sidestream Treatment Alternatives for a Large Municipal Wastewater Treatment Facility

Anaerobic digestion of municipal wastewater treatment sludge releases significant quantities of ammonia and organic nitrogen into sidestream wastewaters. These nutrient loads can be a significant burden to Biological Nutrient Removal (BNR) processes in terms of BNR effluent limitations, oxygen demand and consumption of chemicals including alkalinity and supplemental carbon such as methanol. Sidestream treatment alternatives include separate biological treatment as well as physical/chemical treatment options. A process modeling study was undertaken to compare biological sidestream treatment to ThermoEnergy's Ammonia Removal Process (ARP) which is based on a vacuum distillation process. A full plant process model was developed and used to evaluate the operation and performance of both sidestream treatment options. A large (80 mgd) municipal wastewater treatment facility that accepted and dewatered imported sludge from other wastewater treatment plants was simulated using EnviroSim's BioWin. The model framework included primary treatment, step-feed BNR, sludge thickening, anaerobic sludge digestion, and dewatering of digested sludge as well as imported sludge. Steady state model simulations were performed to characterize average performance and consumables consumption for average loading conditions.