MIDDLETOWN BOROUGH AUTHORITY WASTEWATER TREATMENT PLANT
Abstract:The Authority's 2.2 MGD wastewater system, located in Central Pennsylvania in Dauphin County, serves the Borough of Middletown, the Borough of Royalton and a portion of Lower Swatara Township. Of the total flow received at the plant, approximately six-percent of the flow is contributed by Royalton and approximately fourteen-percent by Lower Swatara Township. The original primary treatment plant with disinfection was built in 1958. The secondary treatment plant and facility expansion were completed in 1976. Biosolids handling improvements were added in 1987. A recent construction project included biosolids treatment facilities to produce exceptional quality biosolids. The existing “wet end” process units include a comminutor and grit removal, primary settling, activated sludge treatment with clarification, chlorine addition for disinfection and effluent aeration prior to discharge into the Susquehanna River. Dechlorination, if needed, is provided by the addition of sodium bisulfite. Phosphorus is removed by adding ferrous chloride.
The biosolids stabilization process consists of aerobic digesters with coarse bubble diffusers. Liquid biosolids are dewatered by a belt filter press and were previously treated with lime prior to land application to approximately 500 acres of DEP approved permitted farm land.
In 1999, the Authority designed new facilities to handle the current and future biosolids generated at the treatment plant. The Authority applied for and received a Pennsylvania Department of Environmental Protection (DEP) Recycle/Reuse Grant for 550,000 to support the proposed project. The constructed project includes a patented alkaline pasteurization rocess consisting of lime addition, mixing and pasteurization of the dewatered biosolids, with the capability to handle up to 1,000 dry tons per year. Lime is added in a ThermoBlender. with supplemental electric heating. The combination of the lime addition and the heating raises the biosolids temperature and pH and reduces the pathogens and odors. The biosolids/lime mixture passes through the Pasteurization Vessel., where the temperature is maintained at 160 °F for a minimum of thirty-minutes to provide for DEP's “process to further reduce pathogens”. The final product is then moved to an enclosed storage building where the material further air dries to approximately forty-percent solids. There are additional facilities to mix in agents such as saw dust, leaf mulch, cocoa shells, etc. to the mixture to provide for additional moisture control and to produce a more aesthetically acceptable end-product.
The biosolids processing facilities include a 2,000 square-foot mechanical process building and a 9,000 square-foot biosolids storage and loading building. In addition to the biosolids processing equipment, the mechanical building houses two air-scrubbing systems, one 6,000 cfm unit for the mechanical building and one 12,000 cfm unit for the storage building. The air scrubbing system is used to neutralize the ammonia-laden off gases from the process prior to discharge to the atmosphere.
The recent project construction and system start-up occurred in early 2001, with a construction cost of approximately 2,150,000, which was financed in part by the DEP's 550,000 grant.
The Class A product is marketed to farmers as a liming agent and home owners as a soil conditioner as part of the Nature's Blend® program. See attached Soil Conditioner Information sheets.
Document Type: Research Article
Publication date: 2003-01-01
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