City of Marshall

The City of Marshall owns and operates the Robert J. Swalwell Wastewater Treatment Facility at 801 Industrial Road. The plant was renamed in 1997 in honor of Bob Swalwell upon his retirement after 43 years of service to the City. The facility currently treats about 1.5 million gallons of wastewater every day. The wastewater originates from domestic and industrial sources within the system's service area, which includes the City of Marshall and some outlying areas, such as Lyon Lake. The plant is in continuous operation and the effluent must meet the requirements of a National Pollutant Discharge Elimination System (NPDES) permit issued by the Michigan Department of Environmental Quality. The 6 member staff at the facility includes a superintendent, 4 operators, and an IPP coordinator. The staff conducts daily analysis and ongoing operational evaluation to ensure continuing adherence to these permit standards. Along with the above duties, staff is responsible for the operation and maintenance of fourteen lift stations located throughout the community. Operations: The plant utilizes an activated sludge process with the addition of ferric chloride for phosphorus removal. The effluent from the plant is disinfected with chlorine and then treated with sulfur dioxide to remove any residual chlorine prior to discharge. Biosolids are stabilized with lime for pathogen control and then land applied to agricultural ground to recycle nutrients. History: The original Marshall Wastewater Treatment Plant was built in the mid 1950's after a directive from the State of Michigan Water Resource Commission to halt sewage pollution of the Kalamazoo River. The first plant provided only primary treatment, including screening, solids settling, and disinfection. The 'sludge' removed in primary settling was anaerobically disgested and then dried in open drying beds. In 1975, a major construction project was undertaken to upgrade the plant to secondary, or biological, treatment and expand the solids handling process. During this project, two new clarifiers and an aeration basin were added. The sludge digesters were converted to storage tanks and a vacuum filter was installed to process sludge which was then hauled to a land fill. In the early 1980's, the City switched from landfilling to land applying the 'sludge'. The process involves subsurface injection of lime stabilized sludge onto agricultural land. Around this time the plant began using sulfur dioxide to dechlorinate the effluent being discharged in the Kalamazoo River. In the 1990's a new term for sludge evolved...we now call it biosolids. In 2000, the efficiency of the plant was improved by an upgrade to the aeration basin. A 'fine bubbler' system replaced the older 'course bubbler' system to improved treatment. A rotary drum thickener was installed to replace the vacuum filter for biosolids processing. The new thickening process removes excess water from the biosolids to minimize the quantity being land applied.