The engineer for the Dick Creek, GA, Water Reclamation Facility expansion project chose to employ a Sequencing Batch Reactor (SBR) system, along with a cloth disk filtration system, because of the limited space available for expansion and the high quality of effluent required by the facility?s water reuse program.
During the evaluation phase, the SBR process was compared to a conventional flow-through treatment plant process. The SBR process was chosen for its ability to perform biological nutrient removal within the batch reactor, without additional basins required as anoxic and aerobic selectors.
Cloth filters were chosen over sand filters due to their larger hydraulic capacity with up to 75 percent less footprint, and improved effluent quality versus that delivered by sand filters. Other advantages to the cloth filters were automatic operation, minimal maintenance, and ease of installation.
The combination of an SBR, with a cloth disk filtration system, allowed for optimal use of the limited available space.
The SBR system at Dick Creek WRF uses two 65 foot circular basins, with water levels that vary from 16.6 feet to 24 feet. The reactors are equipped with retrievable coarse bubble aeration, 50 HP positive displacement blowers, 20 HP mixers, and 14 inch pipe decanters. The system was designed to treat 4200 m3 (1.1 MGD) of wastewater with BOD of 200 mg/l, TSS of 200 mg/l, TKN of 40 mg/l, and total phosphorus of 10 mg/l.
The design and construction of the plant was done with an emphasis on economical future expansion. The screening and grit removal at the headworks as well as the filtration and disinfection systems were sized for 4.0 MGD flow. The post equalization basin was sized for 3.0 MGD and plant piping was sized for expansion to 2.2 MGD. The electrical system was designed for 100 percent expansion. The overall design was based upon expansion of the plant from 1.2 MGD capacity to 2.4 MGD by constructing only one structure, a third reactor basin equal in volume to the original two combined.
Water Reuse
The project area is not eligible for a discharge permit at this time due to a moratorium on discharge permits for wastewater treatment plants in the Chattahoochee River Basin. Therefore the Dick Creek plant is required to use a combination of land application and reuse to dispose of the treated effluent. Thirty-two acres of combined drip and spray irrigation was installed in the initial phase to allow treatment until the flow reached 160,000 gpd. The second phase called for a plant producing reuse quality water to be used as irrigation water on two golf courses and as dust control and process water for a nearby rock quarry and two concrete plants.
Water Reuse
The effluent quality from the plant has consistently attained biochemical oxygen demand (BOD) and total suspended solids (TSS) values less than 5 mg/l, total nitrogen less than 5 mg/l, total phosphorus less than 3 mg/l (without chemical addition), and turbidity less than 2 NTU.
Summary
The combination of an SBR and a cloth disk filtration system to produce high quality effluent for reuse purposes has been proven to work well at the Dick Creek facility. The flexibility, reliability, and small footprint of the system makes it well suited for nutrient removal and water reuse applications. The design of the plant for economical expansion together with its ability to produce effluent far exceeding the requirements imposed by the State of Georgia has make the Dick Creek system a showpiece in Georgia wastewater reuse.
Summary
Evaluation of the plant design, operation and maintenance records, plant performance and safety program resulted in the Georgia EPD awarding the owner with Plant of the Year Award in 1998. The Dick Creek plant is the first privately owned or operated plant to receive the award in the state of Georgia.
