While many wastewater treatment plants are trying to “go green,” the Southside Wastewater Treatment Plant in Vidalia, Ga., has been going green for years.
The plant pumps up to 1.5 mgd of treated effluent onto an adjacent 505-acre tract of loblolly pine trees. It’s an effluent recycling system that helped the plant win the 2008 U.S. EPA Clean Water Act Recognition Award — first place among non-discharge plants. “It was a big award for a little ol’ town in south Georgia,” says operations supervisor Spencer Ricks. “It felt pretty good.”
Ricks works for ESG Operations Inc., Duluth, Ga., the operator of the Vidalia plant and a number of other treatment facilities in Georgia, Mississippi, Alabama and Florida. ESG is in the sixth year of a 10-year operations contract with the city.
A valuable effluent
The Southside treatment plant serves about 15,000 people in Vidalia, as well as a number of key industries, including apparel and aircraft parts manufacturing. It also treats leachate from the Toombs County Landfill.
The plant uses a relatively simple system that relies on natural and physical processes to deliver a valuable effluent. Wastewater is pumped into the headworks through a lift station and passes through dual manual bar screens. Ricks’ staff has modified the screens from the original 1.5-inch slot size to 0.5-inch spaces to improve debris removal. A dumpster contains collected debris.
The screened flow proceeds directly to three 748,000-gallon concrete-lined aeration basins, which operate in series. Each basin measures 100 feet by 100 feet by 10 feet deep and contains two floating Aqua-Jet mechanical surface aerators (Aqua-Aerobic Systems Inc.). These units aerate the contents, maintaining a minimum dissolved oxygen contact of 2 mg/l.
The aerated water passes over the weirs and into a 5-million-gallon earth-lined holding pond, where solids settle to the bottom. The treated effluent is pumped through a 5-foot-diameter tee-assembled stainless steel Johnson intake screen, located in an open wet well. The screen (Johnson Screens) creates a low-velocity flow, decreasing clogging and blocking in lines. Treated effluent then passes to a second 52-million-gallon earthen holding pond, and ultimately into the spray irrigation system.
Back to the land
“The city owns approximately 600 acres next to the plant, surrounding the municipal airport,” explains Ricks. “The land is planted with loblolly pines, and their growth is promoted by the nutrients in the treated effluent.”
The spray field consists of 2,500 spray heads, positioned across 10 separate zones. The 12-inch feed line, 6-inch laterals, and 1-inch lines to the spray heads are all schedule 80 PVC pipe. Each flapper-type Senninger model spray head (Senninger Irrigation Inc.) is capable of broadcasting effluent across a 50-foot radius. Heads are spaced every few rows between the trees.
The Southside staff monitors the quality of the effluent closely before it goes out to the spray heads. At the wet well in the final holding pond, they pull effluent samples through a tap on the distribution main and test for regulated contaminants. They also closely watch the quantity of water being pumped to the irrigation system.
A transducer displays the depth of the pond, and the operators balance the desired depth (around 14 feet) against the amount of water they are permitted to spray per day per zone. “Generally, we water between seven and 19 hours per day, four days a week,” he says. No watering occurs during rainy days.
Ricks’ crew is responsible for operating and maintaining the spray irrigation system, as well as supervising the harvest of trees from the pine forest. “We go into the field every day and record spray head condition, zone by zone, into a spreadsheet,” he says. “We note when a line or head is broken or clogged, and we make the necessary repairs or replacement immediately.”
Spray head condition, as well as spray intensity and direction, are critical to preventing pooling or runoff of the effluent water.
Harvesting the timber
Working with the city and logging contractors, ESG also manages selective cutting on the plot. Trees reach maturity in 10 to 15 years and are then harvested. The revenue goes to the city. Crews then replant the cutover areas with seedlings to assure a sustainable yield and a constant demand for the treated wastewater effluent.
“The nutrients we’re providing with our effluent actually cause these trees to grow faster than similar trees that don’t receive effluent irrigation,” says Ricks.
While the Southside plant received high marks for effluent reuse and sustainability, the EPA award recognized the operation for an exceptional maintenance system, safety and training programs, and overall aesthetics.
Ricks and his staff of Frank Landrum and Phillip Davis (operators), Mark Durden and Chris Campbell (maintenance) and Sean Meyer (technical and administrative support) use a GBA Master Series maintenance system.
There they log preventive maintenance work orders (PMs) for scheduled tasks, and corrective maintenance work orders (CMs) for any reported equipment malfunctions and repairs not scheduled on a PM. The system also tracks parts and labor costs and keeps a record of frequency of completed PMs, CMs and other tasks.
Training and safety are every bit as important. Ricks feels hands-on training is best. “We spend time with new staff people,” he says. “We take advantage of classes offered by the Georgia Rural Water Association, and we train new personnel on the ‘Sac Books’ (California State University at Sacramento wastewater volumes 1 and 2).”
These procedures prepare staff for the state Class 3 operator certification test. Additional coursework and testing through the GRWA leads to higher certifications.
The plant, and indeed the entire ESG organization, is serious about safety (see sidebar). Ricks schedules weekly safety meetings to review proper procedures, and ESG safety coordinator Darrel West holds monthly hands-on sessions with the full crew to review equipment and vehicle operation, and other specific scenarios.
The training and safety programs have been successful. “We’ve had no plant accidents in over five years,” says Ricks. That’s another important aspect of sustainability.
