Stevenson, Alabama is the site of the new Dekalb Jackson WTP, situated, as the crow flies, south and west of Chattanooga Tennessee. Prior to 2008, Dekalb and Jackson counties, and the communities within them, relied upon water purchased from several neighboring Water Districts. An ongoing drought in the region and anticipated future increases in the wholesale cost of water was cause for concern. Also the counties needed to control fluctuations in required water volumes. So the project was launched to provide greater Dekalb and Northern Jackson Counties with a new water treatment system to draw from the Tennessee River and to meet current and future demand for high quality finished water.

The main water source in the area is the Tennessee River. The water often exhibits turbidity spikes over 100 NTU with organics that affect the taste and olfactory perception of the water. Membrane technology was considered favorably based upon its provision of a physical barrier to contaminants and the ability to provide high quality water, two goals difficult to achieve with conventional filtration technologies. Another criterion was to meet the increased regulatory focus on incoming cryptosporidium levels. Working with the consulting engineer, ADL Engineering Services, WesTech Engineering provided an all-inclusive ultrafiltration membrane system--one of the first low- pressure membrane systems from a river water source in the state of Alabama.

Two submersible pumps draw raw water from the river into two pretreatment trains with flocculation tanks and upflow fluidized sludge blanket clarifiers. The water then flows upward to a sedimentation basin. The water is collected by launders and pumped to the ultrafiltration membrane system. The AltaFilter™ UF system is arranged in four banks, each with sixteen modules. The filtered water is then sent to a clearwell for disinfection and distribution. The membrane filtration produces finished water with an average turbidity that consistently measures less than 0.05 NTU.

“We like it from an operations standpoint.” Manager Tommy Bryant says, “The plant is completely automated and is controlled through a PLC interface. So, we can operate the plant from the control room.” “Because the plant and engineers had only to work with one manufacturer for all of their pre-filtration and filtration needs, the project was turnkey, and went smoothly,” says Jake Blattman with WesTech Engineering. "We did address some process challenges early on, but we worked together and the plant is now making clean water according to plan. It is the model for several new projects in the planning stages in the same region.” The system can produce approximately 3 MGD of clean water to the community.