Biosolids Drying Facility Process Improvements

The City of Hagerstown (City) owns and operates a wastewater treatment plant (WWTP), which is capable of treating up to 8.0 million gallons per day (mgd) of wastewater generated inside the city limits and in Washington County.  The City also operates 25 pump stations and a network of wastewater collection system.  With an average flow of approximately 6.0 mgd, the liquid treatment at the plant consists of headworks and preliminary treatment, primary clarification, biological nutrient removal (BNR) treatment for the removal of biological and chemical oxygen demand, phosphorus and nitrogen, and secondary clarification. The secondary effluent is filtered using upflow continuous backwash (UCB) filters, disinfected, and discharged to Antietam Creek via an unnamed tributary. Biosolids produced from the primary and secondary sedimentation processes are co-thickened using a dissolved air flotation thickener and pumped to a sludge holding tank. The thickened solids from the sludge holding tank are pumped to a Pelletizer Facility to generate a dried biosolids product for beneficial use.