Brief Project Description
Grantee: Hampton Roads Sanitation District (HRSD)
Grant: #440-S-09-11 (Nansemond WWTP)
HRSD owns and operates the Nansemond wastewater Treatment Plant (NTP), which provides secondary treatment at the existing design capacity of 30 MGD. The existing NTP consists of preliminary treatment (grit and screening), primary treatment, secondary treatment (3-stage “Virginia Initiative Plant” process, a BNR activated sludge system), effluent disinfection and dechlorination prior to discharging to the James River. Solids handling processes include gravity thickening for primary solids and waste activated biosolids, pre-heated anaerobic digestion, centrifuge dewatering and scum dewatering. Dewatered biosolids are transported to HRSD's Boat Harbor or Army Base WWTP for further treatment and reuse or disposal. Under new nutrient discharge control regulations for the Chesapeake Bay and its tributaries, HRSD has received a combined waste load allocation for nitrogen and phosphorus for its three treatment plants discharging within the James River watershed. Providing nutrient removal at the NTP is a key element for meeting the waste load allocation for the James River and improving local water quality. Under a plan referenced as NTP Nutrient Reduction Improvements, HRSD will upgrade the existing secondary treatment process to a nutrient removal system designed for an annual average total nitrogen effluent concentration of 8.0 mg/l. Facilities included are described as follows.
- Two new 2.7 million gallon aeration tanks to upgrade to 5-stage BNR treatment.
- Modifications to existing aeration and anaerobic/anoxic tanks to enable 5-stage BNR treatment.
- Modifications to existing Centrate Recycle/Nitrate Recycle (CRCY/NRCY) pump station.
- New supplemental carbon feed facility.
- Replacement of secondary clarifier sludge collection mechanisms in Clarifiers No. 1-3 (50% grant eligible).
- New blowers, standby power and switchgear (partially grant eligible).
- Upgrades to electrical systems and instrumentation and control (90% grant eligible).