In the old days, several communities in Alabama’s St. Clair County depended on individual wells for drinking water — sources that weren’t always reliable because of droughts, over-drafting and water-quality issues.

Yet economic development and population growth in the area, including a major Honda automobile production facility, depended on the availability of clean water.

Today, the communities are served by a state-of-the art regional water treatment plant and system. Source water is drawn from an abandoned rock quarry fed by the Coosa River, and the treatment facility includes the state’s first Superpulsator upflow clarifier (Infilco Degremont) applied to drinking water. It’s an innovation that saved on capital cost and reduced the plant’s equipment footprint.

Four entities — Springville, Pell City, the Town of Odenville and St. Clair County — gave up their water systems to form a regional district, says Steve Cawood of the engineering firm Goodwyn, Mills and Cawood, which designed the plant and system.

Design innovations

The district was formed in 2003. After eight years of planning, grant applications, permitting and construction, the new Coosa Valley Water Treatment Plant began operating in 2011.

It is operated by the private firm ClearWater Solutions, a sister company to Goodwyn, Mills and Cawood. The plant manager is Tim Mitchell, whose team includes Casey Cambron, Joseph Burt, Joel Casey and Lamar Shirley, operators; and Brian Moore, trainee.

Two things about the plant excite Mitchell and his staff. For one thing, the plant is completely enclosed, warding off summer heat and humidity and occasional winter cold snaps that could cause freezing issues with feed lines and other equipment.

For another, designers built the treatment process around the Superpulsator, which combines flocculation, coagulation and upflow clarification in a single compact step. “Excellent” is how Mitchell describes its operation, although his team has had to tinker with the water chemistry to compensate for the low-turbidity source water.

The 200-foot-deep quarry, fed by the river and a series of springs, is full of relatively clear water. “The water is so clear,” Mitchell says. “It can range between 1 and 4 NTU. That can make it difficult for the particles to bond, and we actually need to add more chemicals to coagulate the floc.”

Ferric sulfate is added to the raw water to increase the precipitation of particles. “We use polymer to keep everything attached,” Mitchell says. “At certain times of the year, we do a little prechlorination in order to get even better coagulation.”

Compact system

The Superpulsator consists of a rapid-mix zone, followed by a vacuum chamber and then a series of inclined settling (lamella) plates. Coagulated water from the rapid-mix system enters the vacuum zone and then is uniformly distributed to the basin containing the inclined plates. A sludge blanket, maintained about midway in the plate basin, attracts and collects solids as the water passes up through it. Powdered activated carbon aids in clarifying the water by absorbing organic material.

The vent valve assembly on top of the vacuum chamber opens and closes, drawing water in and out of the chamber. As a result, the sludge blanket contracts and expands (pulses), combining the flocculation, clarification and sludge collection steps into a single process. “In our system, the sludge blanket is about 24 inches thick and expands and contracts every 15 seconds,” Mitchell says. “Because our turbidity is so low, we don’t generate a large volume of sludge.”

Solids wasted from the sludge blanket and filter backwash water are pumped to two lagoons operating in parallel, each with 1-million-gallon capacity. Water discharged from the lagoons is dechlorinated and pumped back to the Coosa River.

Back at the Superpulsator, clarified water is collected uniformly across the length of the settling area and is passed through 1.5-inch holes in PVC pipe into a trough that feeds subsequent treatment processes. Filtration is the next step. Three 750 gpm dual-media filters (Leopold), consisting of granular activated carbon and sand, are rated for 2 gpm per square foot of filter surface area. Bed depth is 72 inches. The filters are equipped with a Leopold control system.

After filtration, the product water is disinfected with sodium hypochlorite at 2 ppm and is pumped to a 750,000-gallon clearwell. From there, maintaining a chlorine residual of 1.5 to 1.75 ppm, it travels to the four community water systems. The district maintains 227 miles of distribution lines, two ground storage tanks and one booster pump station. Master Meter smart flowmeters at each connection point yield continuous measurements of the flow being used by each community. The meters feed into the district’s SCADA system (MR Systems), and the communities are billed quarterly based on consumption.

Quick study

Although the Superpulsator technology was new to the Alabama water treatment profession, the Coosa Valley plant staff picked up on it quickly. “We conducted special training when we first started,” says Mitchell. His staff consulted the operations manuals and simply practiced to achieve successful operation.

“Six months into it, we were producing high-quality water,” says Mitchell. “We’ve never been out of compliance.” Staffing seven days on, seven off, each operator takes 12-hour shifts. One extra person helps in the distribution system.

The quality of the raw water was critical. “We needed to be patient with the process to allow it to sort of create itself,” says Mitchell. “With low turbidity it takes awhile to create the sludge blanket; with NTUs of 5 or above the blanket creates itself much faster.”

The staff continues to experiment. “We wash down the clarifier basin once a year,” says Mitchell. “The next time we wash it, we’re going to try Bentonite clay as a binding agent to try to expedite the process of building the sludge blanket. Make it dirty in order to clean it, in other words.”

The demand for clean water in St. Clair County is only expected to increase, so the district is expanding the treatment plant capacity. The filter rate will be increased from 2 to 3 gpm per square foot of filter surface area, enabling the plant to produce up to 5 mgd. The project is expected to deliver additional water the district can sell to outside customers, keeping rates for existing customers as low as possible.

It’s the next phase of an idea that blossomed just over a decade ago and set up area communities and residents for a future of abundant water.

More Information

Goodwyn, Mills and Cawood - 334/271-3200 - www.gmcnetwork.com

Hach Company - 800/227-4224 - www.hach.com

ILFILCO DEGREMONT - 804/756-7600 - www.degremont-technologies.com

Leopold - a Xylem Brand - 855/995-4261 - www.fbleopold.com

Master Meter, Inc. - 800/765-6518 - www.mastermeter.com

MR Systems, Inc. - 678/325-2800 - www.mrsystems.com

ProMinent Fluid Controls, Inc. - 412/787-2484 - www.prominent.us