Henrico County Water Reclamation Facility - A Multi-Phased Expansion
Client: Henrico County
Location: Henrico County, VA
Hazen and Sawyer was contracted to expand the capacity of the County of Henrico’s Water Reclamation Facility from 45 mgd to 75 mgd in multiple design and construction phases. This $100 million dollar project was completed in an aggressive five-year timeline. The existing 45-mgd plant had two flow trains; pure oxygen tanks and dissolved oxygen tanks. The two plants were combined with the new facilities to operate the plant as a single sludge plant (all BNR tanks with dissolved air) in the 75 mgd expansion. The plant was also upgraded to meet Enhanced Nutrient Removal standards, averaging total nitrogen effluent concentrations of under 5 mg/L.
Project Outcomes and Benefits
- BioWin™ modeling was used to optimize facility design and determine how the plant would perform under a wide range of flow conditions.
- Hydraulic modeling of both interceptor and outfall identified the need for a second outfall and ensured the plant’s ability to meet capacity requirements of up to 150 mgd.
- Full-scale testing of multiple carbon sources for the ENR process.
- The new Biologic Nutrient Removal (BNR) facilities were designed to meet a total nitrogen limit of 5 mg/L, with the flexibility to meet even lower limits as regulatory requirements evolve.
Hazen and Sawyer assisted Henrico County in the implementation of a major ENR upgrade to its Water Reclamation Facility in a multi-phased manner. The plant is located east of Richmond, Virginia and discharges directly into the James River, which eventually discharges into the Chesapeake Bay.
Major services provided for this project include process optimization and preliminary engineering. Process optimization included bench-scale modeling to confirm initial wastewater characteristics and determine kinetic parameters for input into the BioWin BNR model. The BioWin model was utilized to determine facility design and predicted how the plant would perform under various flow conditions. Preliminary engineering included hydraulic analysis of influent interceptor into the plant site to determine capacity. Similar analysis was performed on the plant outfall interceptor to the James River.
The multi-phased implementation included:
- New fine screens and grit removal facilities, sized for 150 mgd (twice the dry-weather flowrate). A new septage receiving facility was also included.
- Four new BNR tanks, five 160-foot diameter secondary clarifiers, two Recycled Activated Sludge pumping stations, new effluent disinfection facilities, new plant SCADA system and hydraulic distribution channels for BNR tanks and secondary clarifiers.
- Rehabilitation and expansion of sludge facilities, including a new blend tank, new membrane covers for the existing three anaerobic digesters, a new anaerobic digester, new external pump mixing systems for all four digesters, new gravity belt thickeners, three new high solids centrifuges and new polymer system.
- New effluent deep bed filter, chlorine contact tanks, odor control facilities, and conversion of the existing oxygen tanks to dissolved aeration.
- Installation of 8,800 feet of new 96-inch diameter outfall, increasing discharge capacity to 150 mgd.
- New Laboratory addition and HVAC modifications to the existing Administration Building.
- New 5-stage BNR facilities to provide enhanced nutrient removal to meet the limits of technology. These facilities include optimized methanol dosing.
For more information on this project, or to discuss a similar project in your area, contactRobert DiFiore, P.E. at firstname.lastname@example.org