The Danville Sanitary District (District) is a conventional activated sludge wastewater treatment plant with a design average flow of 16 million gallons per day and a design maximum flow of 24 million gallons per day.  The plant is permitted to discharge effluent to the Vermilion River according to the requirements of its National Pollution Discharge Elimination System (NPDES) Permit Number IL0020788 as issued by the Illinois Environmental Protection Agency.  The NPDES permit specifies the design flows and allowable concentrations of nutrients and solids in the effluent, in addition to other parameters.

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Currently, the plant does not have discharge limitations on total Nitrogen and total Phosphorus in its effluent, although those parameters are monitored and reported.  The Nitrogen and Phosphorous parameters are going to have increasingly stricter limitations which will require modifications to the treatment processes as the EPA provides further protection for the Gulf of Mexico hypoxic zone.  The District will need to be in full compliance with these regulations by 2035.  The EPA has been communicating these pending changes, as they will require significant capital investments.

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