O’Brien & Gere was selected to complete preliminary engineering, final design, construction assistance, and operational assistance phases associated with addressing Enhanced Nutrient Removal (ENR) requirements at the Harrisonburg-Rockingham Regional Sewer Authority (HRRSA) North River Wastewater Treatment Facility (WWTF), in Mt Crawford, Virginia. The Project will expand the average flow treatment capacity of the WWTF liquid treatment processes from 16 MGD to 22 MGD, address hydraulic peak capacity requirements (60 MGD) for expansion, upgrade the WWTF to achieve ENR, and update and renovate other WWTF facilities.

The WWTF was upgraded to Biological Nutrient Removal (BNR) as part of the previous WQIF-funded grant program. Current goals are 8 mg/L Total Nitrogen (TN) and 1.5 mg/L Total Phosphorus (TP). The VPDES Permit was renewed in April 2006. As part of new Virginia nutrient removal regulations, the HRRSA North River WWTF is on the Significant Dischargers List and has been assigned a load cap. When expanded, the regulations require treatment technology capable of 3 mg/L TN and 0.3 mg/L TP, or ENR. Also, with expansion, the peak design capacity will increase from 40 to approximately 60 MGD at 22 MGD average. Hydraulic de-bottlenecking of the existing facility is required along with ENR upgrade improvements.