Henrico County Water Reclamation Facility - A Multi-Phased Expansion
Hazen and Sawyer was contracted to expand the capacity of Henrico County’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.
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. Installation of 8,800 feet of new 96-inch diameter outfall increased discharge capacity to 150 mgd.
- Full-scale testing of multiple carbon sources for the ENR process.
- 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.
Capacity Expansion on a Tight Schedule
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.