Johnston County Commissioners will use money in their sewer fund to pay a half million dollars for an additional 1,000 pounds of total nitrogen allocation.
The Johnston County Wastewater Treatment Facility has an effluent limit of 71,447 pounds per year of total nitrogen (TN). Nitrogen is allocated on a mass basis rather than concentration. The current treatment plant is rated at 9.5 million gallons per day but a 4 million gallon per day (MGD) expansion is under design.
The existing TN allocation should be sufficient for a plant up to 11.5 MGD, but to received a modified permit from the National Pollution Discharge Eliminination System (NPDES) which regulates water pollution the county will need additional nitrogen allocation to increase the flow.
The County recently learned a company had placed 1,000 pounds of TN for sale at $500 per pound.
This month, commissioners agreed to purchase the nitrogen allocation from Phillips Plating Company, Inc. for $500,000. Previously, in 2007, the county paid $490.80 for 1,645 pounds of TN allocation.
Because of Johnston County’s location along the Neuse, a transport factor of 50 percent is applied to the prucahse and the value of the TN allocation will be 2,000 pounds per year, according to Chandra Coats, Director of Johnston County Public Utilities.
The county plans pursuing lease arrangements or purchasing nutrient offset credits through mitigation banks to meet future TN requirements from the NPDES permit program