by Phillip Read
Located in southeastern Georgia, Nashville is the seat of Berrien County and provides water and wastewater services to approximately 1,940 households. The aging wastewater treatment plant and land-application spray fields had become undersized due to growth in the area and also suffered from large volumes of infiltration and inflow during heavy rains. A complete system upgrade had become necessary to manage the issues facing the city’s wastewater service.
The Georgia RCAP team (part of the Southeast Rural Community Assistance Project, the Southeast RCAP) assisted the city in the preparation of its Clean Water State Revolving Fund loan application, including all supporting documents. The loan the city received funded the construction of a new, advanced wastewater treatment facility. The total amount of funding leveraged for the project due in part to the work of the Georgia RCAP staff is $6.2 million. The project began in January 2010 and is scheduled to be concluded in 2013.
Technical specifications
Wastewater pumped from the influent pumping station will receive preliminary treatment at a new or rehabilitated headworks consisting of fine screening and grit removal. Flow will then be by gravity through a splitter box that will feed the biological treatment process. Flow to the biological process will be by automatic control during the fill cycles. Flows in excess of the 1.0 MGD design flow will be directed to the aerated lagoon for treatment. From there, the flow will be directed to either the LAS storage lagoon for treatment in the land-application system or to what is now the facultative lagoon, which will be converted for use as off-line flow equalization. This flow can then be returned to the new biological treatment process for treatment and discharge.
The plant will consist of a two-tank, sequential batch reactor (SBR) process to provide oxidation of carbonaceous BOD and nitrification of influent nitrogen. The SBR sequencing will be modified to allow maximum biological uptake of phosphorus. Additional phosphorus removal will be by chemical precipitation using alum. Decants from the SBR will be equalized and polished by tertiary filtration. Disinfection by UV and post-aeration will be provided prior to discharge to the Withlacoochee River.
Wasted sludge will be aerobically digested, dewatered and transported to a sanitary landfill for disposal. Each SBR tank will use fine bubble diffusers. A dissolved oxygen meter will be provided in each tank to allow for the option of automatic or manual control of air flows for process optimization.
The project was divided into two phases consisting of the rehabilitation of existing facilities and new construction.
Phase one addresses the rehabilitation of the influent pump station and the land-treatment system. The plant’s operators reported that the existing pumping station had been able to handle peak flows during heavy rainfall periods. However, the facility is aging, equipment (pumps, valves and associated piping) and controls need replacement. There will also be a number of upgrades that will improve the overall operation of the land-application spray fields. These include:
- removing accumulated sludge in the aeration lagoon
- rehabilitation of the spray fields
- replacing the floating baffle in the aerated lagoon
- repairing or replacing defective aerators
- rerouting piping to maximize storage capacity
- screening and grit removal of the influent
Phase two addresses needs in the areas of screening and grit removal; influent sampling and flow measurement; flow direction; the construction of the wastewater treatment facility itself; biological treatment; chemical storage and feed; tertiary filtration; sludge handling and removal; disinfection; post aeration; effluent sampling/monitoring; plant drains; discharge piping; and standby power/redundancy.
The Georgia RCAP staff worked closely with the consulting engineer, city clerk and council, funding agency personnel and the state environmental agency representatives to prepare the application, obtain funding for the project, and to prepare requests for proposals for local contractors. The Georgia RCAP team will continue to assist with post-award requirements and reporting and will monitor the construction as it progresses.
Read is the Director of the Georgia Rural Community Assistance Program, part of the Southeast Rural Community Assistance Project, the Southeast RCAP [1].