Brief Project Description
The existing Broadway Wastewater Treatment Plant (WWTP) has a permitted design flow of 1.923 MGD, which provides secondary treatment via three synthetically lined basins operated in series. Basin 1 and 2 include static tube (coarse bubble) diffused aeration. Basin 3 is used for storage and effluent pumping to farm irrigation sites; chlorine disinfection and dechlorination follow conveyance of the effluent.
The existing plant serves the Towns of Broadway and Timberville, along with Pilgrims Pride and Cargill Foods. Included with the WWTP upgrade is a plant expansion to 2.923 MGD, in order to also serve the Town of New Market and provide for regionalization. A Preliminary Engineering Report (PER) for the expansion was submitted to DEQ (most recently dated: May 2008) to address the expansion and wastewater process needs. Two alternative biological processes (Bardenpho and Biolac) were evaluated for the treatment facility. Based on the capital and annual cost comparisons along with expected treatment performance, the engineer recommended the new WWTP utilize a single train Bardenpho process followed by secondary clarification, chemical addition of metal salt and carbon, up-low filtration, force main outfall, and solids handling/dewatering.
This project consists of various facilities included in the PER which are intended to achieve nutrient compliance. Processes being installed, and their grant eligibility as Nutrient Reduction Technology (NRT), are described as follows.
Preliminary Treatment (not grant eligible): New pumping and screening of raw wastewater.
The biological process will include converting the existing facultative lagoon #2 to a Bardenpho process by the addition of HDPE suspended baffle curtains and fine bubble, floating aeration. Mixers (respectively 4 and 6) will be added to the anaerobic zone and pre-anoxic zone created by the baffle curtains. Nitrified recycle (4.5Q) pumping by variable frequency drive pumps is also included.
Two 80 foot diameter circular clarifiers are proposed to provide a conservative hydraulic loading of 300 GPD/sf due to the high hydraulic retention time and biosolids with poor settleability. Activated sludge will be returned from the underside of each clarified to a manhole/pump station adjacent to the unit.
UV Disinfection (not grant eligible) and effluent pumping
Solids handling and Dewatering (partially grant eligible): The solids handling process will include two new 300,00 gallon aerobic digester tanks and a 2 meter belt filter press.
Chemical Feed (grant eligible): Bulk chemical storage and feed facilities are proposed for alum to precipitate phosphorus, magnesium hydroxide for alkalinity control, and supplemental carbon for denitrification.
Effluent Filtration (grant eligible): 4 cells of granular media filters are proposed for the project. Each cell will be up-flow (continuously backwashed) and consist of 3 modules for a total of 12, which equals 600 sf. The proposed surface loading rate is 3.42 GPM/sf at average daily flow.
Electrical System Improvements (partially grant eligible): The wastewater treatment plant will include a new onsite standby generator and switchgear building, in the event electrical service is disrupted.