The Doswell Virginia Wastewater Treatment Plant was built to handle water treatment for the Bear Island Paper Mill that began operations in 1979, and the increasing demands from the Paramount Theme Park (formerly King’s Dominion). The demands at this facility have continued to increase as more residents moved into the area. A Natural Gas Power Plant built in 1991 also significantly increased demand. The current wastewater treatment capacity of this facility is 1MGD (one million gallons per day). Waco successfully completed two projects here, greatly improving existing plant operations while providing for future expansion.
WIP III Upgrades for the Doswell Wastewater Treatment Plant
In 2023, Waco began the WIP III Upgrades project, which included the construction of a denitrification process to meet new ENR (Enhanced Nutrient Removal) regulations. These regulations were implemented by Virginia’s DEQ to further remove nitrate-nitrogen from water discharged into the North Anna River, within the Chesapeake Bay watershed. Because this was an existing operating facility, all work was performed while maintaining flow through the plant. Power and existing communications systems (SCADA) had to be kept active throughout the course of the project until the new systems were brought online.
To accomplish these new requirements at Doswell, Waco renovated the existing aeration basins by installing a new aeration system, complete with blowers, piping, diffuser grids and intermediate baffle walls. The existing blower building adjacent to the basins was converted into an electrical room that housed control panels, VFDs and electrical gear for the new equipment. Repairs were also made to the existing primary clarifiers by converting them into pre-anoxic tanks with separate bubbler systems. A new cast-in-place splitter box was installed upstream, with slide gates that direct the flow to each basin. Waco self-performed all concrete work, above ground mechanical piping and equipment installation, and managed the underground piping, electrical, HVAC, and SCADA upgrades.
Downstream of the aeration basins, existing underground piping was modified to add an intermediate pump station (including two pre-cast wet wells and valve vaults) that would pump flow into the new Denitrification facility. A pre-cast overflow vault was also added to the main line so the plant could bypass the pump station and denitrification facility during peak flow periods to prevent the facility from flooding. Waco installed a new concrete pad for access to the wet wells and valves vaults, along with the wet well pumps, piping and valves.
A 4,500 SF pre-engineered metal building was erected to house the denitrification equipment, consisting of sixteen skid mounted tanks (4 tanks/ skid), a 4,000-gallon polyethylene clear well, blowers, pumps, and interconnecting piping. A new electrical room supported the new system and related components. Waco installed the foundation pad for this facility and managed the installation of the building, plumbing, electrical, structural platforms, HVAC and controls. Once the structure was erected and dried in, Waco installed the skid mounted tanks, clear well and interconnecting piping and successfully coordinated with all parties to bring the new system online.
To support the new Denitrification process, separate buildings were constructed on site for methanol and aluminum chemical feed. The methanol facility consisted of a pre-engineered metal building to house the transfer and chemical pumps, with an electrical room and a fire suppression system – all of which were connected to two stainless steel methanol tanks in a containment basin adjacent to the building. The aluminum facility consisted of a separate pre-engineered metal building that housed chemical pumps, electrical gear and controls – all connected to a fiberglass storage tank in another containment basin adjacent to that building. Waco self-performed all concrete work including the building foundations and containment basins for the storage tanks, and installed the tanks, piping and equipment.
Downstream of the denitrification facility, a post-aeration structure was added to the existing effluent line. This consisted of a 20-foot deep cast-in-place structure with slide gates, blowers and aeration diffusers. Waco installed a temporary bypass system to maintain the flow during the construction. Waco self-performed the concrete work and installed the blowers, diffuser piping and slide gates.
The project also included upgrades to the existing control building with a new motor control center and associated panels, and a new backup power generator. In addition, the entire SCADA system was upgraded with a new communication loop throughout the entire site. As each new system was brought online, Waco oversaw the coordination to ensure a successful operation.
While on site, Waco was also requested to rehabilitate an existing secondary clarifier that had been out of service for years. This work involved demolishing the existing center column, arms and bridge and replacing it with new components.
Structures and Equipment installed:
- Splitter Box – (1) new Splitter box structure with (2) slide gates and associated piping and valves
- Aeration Basins- (2) 30 HP blowers, (2) 20 HP blowers, (2) 25 HP rotary lobe pumps, all new aeration headers and piping, new instrumentation also converted old blower building to an electrical room with new VFDs and controls.
- Intermediate Pump Station- (2) precast wet wells, (2) precast valve vaults and (4) 8.5 HP submersible pumps with associated piping, valves and controls
- Denitrification- (1) 4,500 SF pre-engineered metal building, (4) pre-fabricated filter skids, (1) backwash pump and blower skid, (1) 4,000 gal. clear well, with associated piping, valves and instrumentation. New steel platform around filter skids, HVAC in building and attached electrical room with VFDs, power panels and controls.
- Post Aeration- (1) new post-aeration structure w/ (2) 3HP blowers, associated air piping and valves and (6) slide gates
- Methanol- (1) 550 SF pre-engineered metal building with (2) 5,500-gallon stainless steel storage tanks, (4) ½ HP diaphragm chemical metering pumps, (2) 2-HP transfer pumps, (1) chemical sump pump, with associated piping, valves and instrumentation, new HVAC, fire suppression system, and electrical room with VFDs, power panels and controls
- Aluminum Sulfate- (1) 250 SF pre-engineered metal building with (1) 6,000 gal. FRP storage tank, (4) peristaltic tube metering pumps, (1) chemical sump pump, new HVAC, power panels and controls
- Existing Control Room – renovated existing control room with new MCC, new entry doors and replaced existing generator with new 600kW generator.
- Significant site work, all new underground piping between buildings and about 2,000 LF of new underground duct banks
- Insulation system for methanol tanks and piping.
Project Manager: Dan Coon
Superintendent: Rich Foster
Project Engineer: Will Wake
Project Value: $18.3 MM
Doswell WWTP Belt Press Replacement
Waco was also awarded the Doswell WWTP Belt Press Replacement contract, which was completed during the construction of the WIP III Upgrades project. This project included the installation of a new belt filter press, polymer system, and sludge cake pump in the existing Belt Press building. These upgrades helped improve the dewatering process and reduce the sludge volume produced at the plant, ultimately reducing costs of storage and transportation of sludge. Coordination between projects was required as the existing sludge pumps feeding the Belt Press received new VFDs as part of the WIP III Upgrades project. Waco successfully coordinated all parties involved to install the new equipment, controls and communications, to improve the efficiency of the system.
Project Manager: Matt Moore
Superintendent: Rich Foster
Project Engineer: Will Wake
Project Value: $417,000