Brief Project Description
Grantee: Stafford County (Little Falls Run WWTF-Phase I)
Stafford County’s Little Falls Run Wastewater Treatment Facility (LFR-WWTF) was built in 1991 and includes two 4.0 million gallon per day (MGD) Schreiber treatment trains (activated sludge) operated as a Biological Nutrient Reduction (BNR) process capable of total nitrogen (TN) reduction to an annual average concentration of 8.0 mg/l. The facility also includes headworks, an alum feed system and chemical mix tank for total phosphorous (TP) removal, two secondary clarifiers, a secondary effluent screw lift pump station, a tertiary filtration system, ultraviolet disinfection, a sludge holding tank, four aerated sludge storage silos, and a centrifuge sludge dewatering system. Dewatered sludge is stored and then disposed at a municipal landfill. The plant is certified to operate at an average daily flow of 4.0 MGD and utilizes one Schreiber train at a time. TN reduction capability was grant-funded under a prior WQIF Agreement (#440-S-00-04); TP removal was not funded.
At present, LFR-WWTF is nearing its design capacity, as currently operated with alternating Schreiber trains. Much of the equipment is also at the end of its design life. To expand the plant and meet its waste load allocation, Stafford County plans to upgrade in two phases. The project funded under this Agreement addresses Phase I and will upgrade the facility from BNR performance to Enhanced Nutrient Removal (ENR) treatment capable of attaining annual average effluent TN of 5.0 mg/l and TP of 0.30 mg/l at a design flow of 6.0 MGD*. Phase I upgrades will change the Schreiber trains to work in parallel with the addition of cyclical aeration controls to improve the nitrification/denitrification process. The internal recycle rate will also be increased to accommodate greater nitrate removal.
Project components include:
- Removal and replacement of existing blowers and diffusers (reactor basins and sludge facilities)
- Install additional blowers and diffusers (reactor basins and sludge facilities) with associated piping
- New sludge storage silos (4)
- New instrumentation and electrical upgrades
- Headworks modifications to handle additional flow (not grant eligible)
- Site work and demolition
- New back-up generator
- Ultraviolet disinfection upgrades (not grant eligible)
- Re-routing of outfall (not grant eligible)
NOTE: *LFR-WWTF is hydraulically sized for 8.0 MGD in the Phase I project. However due to an existing VPDES Permit tier at 6.0 MGD and a regulatory requirement for more stringent nutrient reduction treatment at 8.0 MGD, the WQIF grant and the Certificate To Operate (CTO) will recognize 6.0 MGD as the design flow until the Phase II project (upgrade/expansion to meet all VPDES permit limits at 8.0 MGD design flow) is completed. The WQIF grant is pro-rated accordingly.