Ash generation is the byproduct of the regeneration of spent PAC in the WAR unit of a PACT/WAR system. Successive regenerations of PAC have resulted in ash accumulation in the system. Operational and design data from the East Burlington Wastewater Treatment Plant, NC were used to verify and test the effectiveness of a constant input, steady state model for simulating this phenomenon. The model performs mass balances for four different solids (Biomass, PAC, Light ash, and Heavy ash) around each essential unit of the system. A sensitivity analysis identified WAR unit efficiency, fraction of biomass converted to Light ash at the WAR unit, fraction of Heavy ash lost to the WAR unit, and secondary clarifier efficiencies to remove Light and Heavy ash to be important process parameters. Results of a 12-month and a 2-month simulation runs indicate that the model is capable of predicting percent increase in average mixed liquor ash concentrations and has potential as a tool for design and decision making. It is unable, however, to follow the variation present in reported data of a system that exhibits periods of unsteady state conditions, as in the case of Burlington.