Brief Project Description
Under a proposal for nutrient removal cost share, plant hydraulic capacity expansion will be expanded to a permitted flow of 12.6 MGD under Phase 2A and the treatment processes will be upgraded to achieve the additional objective of State of the Art (SOA) nutrient removal under Phase 2B.
Phase 2A elements and components consist of the following:
Existing Influent Pump Station Hydraulic Improvements
New Headworks Structure
2 - New Primary Clarifiers
Upgraded Primary Clarifier & Aeration Basin Distribution Chamber
2 – New Secondary Clarifiers
Upgrade of Chlorination & Dechlorination Facilities
Chlorine Contact Basin Improvements
Upgrade of Gravity Filters
Associated Yard Piping
As part of this project, a new head works facility will be added to expand the hydraulic capacity of the plant. The facility will operate in parallel to the existing head works, and will contain a mechanical bar screen and grit removal chamber. Two additional 70-foot diameter primary clarifiers will be constructed, and the primary clarifier distribution box will be reconfigured. Primary sludge and scum pumping will be upgraded. Two influent pumps will be replaced. Ferric chloride will be added to the new primary clarifiers to precipitate soluble phosphorus. The septage disposal facility will be retained at present; however, the SOA upgrade was not designed to treat septage. Septage will continue to be accepted until the plant reaches a future capacity, where the additional septage loads can not be treated.
Phase 2B elements and components consist of the following:
Retrofitting of existing Aeration Basins
Construction of 2 additional Aeration Basins and Secondary Anoxic Re-aeration Tank
Permanent Carbon Feed System and Chemical Feed System Upgrade
Expansion of Gravity Filter Capacity
Expansion of Sludge Storage and Processing
2 – New Gravity Sludge Thickeners
Upgrade of Plate Press Control System
In order to accomplish SOA nutrient removal, the biological system will be converted to a 5-stage Bardenpho configuration (anaerobic, anoxic, aerobic, anoxic, aerobic zones). The three existing aeration basins (#1, #2, #3) will be converted and two new aeration basins (#4, #5) will be constructed. Two new secondary anoxic tanks (#1, #2) will be constructed and will operate as a common denitrification reactor for all five biological trains. The conversion of the existing aeration basins will include the installation of submersible mixers and fine bubble diffusers.
A new supplemental carbon storage and feed system will be constructed. Acetic acid will be added to the second anoxic zone on a contingency basis as a supplemental carbon source to enhance the denitrification process. New ferric chloride tanks and pumps will be installed to supply the primary clarifiers, the secondary clarifiers, and the gravity filters. The polymer make-down and transfer system will be replaced.
Two 85-foot diameter secondary clarifiers (Secondary Clarifiers 5 and 6) will be constructed to handle the increased plant flow and to provide operational flexibility. Provisions for polymer addition will be included. A new clarifier splitter box (for Clarifiers 4, 5, and 6) will be constructed. The clarifier splitter box will utilize overflow weirs to divide the flow between the six clarifiers. Slide gates will be provided to shut off flow to each clarifier. One new return activated sludge (RAS) pump will be installed, and the two existing waste activated sludge (WAS) pumps will be replaced with two larger capacity pumps.
Filtration capacity will be expanded by converting the two, existing traveling bridge gravity sand filters to a cloth filter media designed to handle high flows and high solids loading excursions. The flow will continue to be conveyed by gravity from clarifiers to filters. The disinfection system will not be changed, but the storage building will be expanded and additional storage tanks will be installed. The existing post aeration cascade steps will be widened to accommodate the higher hydraulic capacity and new effluent flow meters will be installed to provide reliable measurements during times of high flow.
Two new gravity thickeners (#3 and #4) will be constructed and the existing flow distribution box will be reconfigured to accommodate the new tanks. The four sludge transfer pumps will be replaced with five larger capacity pumps. One new aerated sludge holding tank will be constructed and will contain four cells. The cells will have removable covers to contain odors but allow maintenance access. Three new air blowers (two plus one spare) will be installed, along with coarse bubble air diffusers. The existing plate and frame dewatering presses will be upgraded with new controls. The dewatering building will receive a dedicated drain line and a new acid storage tank. The discharge neutralization manhole will be replaced, and the soda ash system will be converted into a lime feed system