It might not have been the parting of the Red Sea, but the early-morning chlorine contact chamber diversion at the Middle Oconee Water Reclamation Facility in Athens-Clarke County, Ga., was pretty dramatic.
While continuing to operate and maintain compliance during a major construction program, the plant staff and contractor needed to stop plant flow for several hours so one of two chlorine contact chambers could be taken down for conversion to UV disinfection.
“We worked on a plan several weeks in advance,” says plant operations supervisor Tim Holder. “Everyone knew exactly what to do.” Without the luxury of an equalization basin, Holder’s team emptied one of the oxidation ditches and drew down clarifiers to provide extra storage capacity. Then, in the middle of the night, they stopped flow and the contractor cut and capped pipes, isolating one of the chlorine chambers and started its demolition.
“There was no water leaving the plant for eight to nine hours,” Holder says. “The contractor (Western Summit of Colorado) worked super fast. When the sun came up the next day, we were done.”
It’s just one of many on-the-fly adjustments the staff has made as the plant upgrades treatment to add phosphorus removal and increase capacity from 6 mgd to 10 mgd. It’s also an example of how plant management and the contractor work together. “We’ve had an excellent relationship,” says Holder. “It’s almost like they’re wastewater treatment operators themselves.”
The Middle Oconee plant project is one of three the Athens-Clarke County public works department is completing at a total cost of about $49 million. The other two are the North Oconee plant, and the Cedar Creek plant.
The original Middle Oconee plant dates to the late 1960s, when it was a trickling filter operation. It was converted to activated sludge in 1990. Today, wastewater travels through a 106-mile sewer system serving a 36-square-mile drainage basin and about 35,000 residents.
When the plant is fully upgraded, the flow will be boosted by four submersible pumps (Weir Specialty Pumps/WEMCO) to a headworks containing JWC 3-mm band screens and a Eutek grit removal system (Hydro International). Then it will pass through an anoxic-anaerobic biological basin for phosphorus removal.
From there the flow will be split among three 2-million-gallon Orbal oxidation ditches (Siemens) for further biological treatment. Three existing 80-foot-diameter clarifiers are being joined by a fourth, 120 feet in diameter. TrojanUV units will disinfect the effluent before discharge to the Middle Oconee River, which flows to a recreational lake downstream.
Just recently, Athens-Clarke County began composting its biosolids at the local landfill. At the Middle Oconee WRF, waste solids will be digested in a coarse-bubble aerobic system, followed by centrifuges. Existing units are Sharples (Alfa Laval), and a new Andritz centrifuge is being added. Plant staff can use centrifuges for thickening and dewatering.
The new plant will have a sophisticated SCADA system, tying all three treatment plants together. Transdyn is the system integrator. The plant staff in addition to Holder includes superintendent Mark Roberts (retiring soon); operations coordinator Dave Bloyer; operators Robert Barrington, Jack Brehm, Charles Cowart, Jimmy Elder, Pat Freeman, Jameson Goolsby, Rex Hatfield, Jim Hanson, Scott Jones and Bomani Wilson; maintenance mechanics Clarence Burgess and Bill Lumpkin; and electricians Jon Cline and Richard Young (shared with the other two treatment plants).
Improving and expanding treatment while working around continuing operations has had its share of challenges. Holder and his staff have had to deal with several other issues involving return activated sludge, digesters, and the dewatering process.
“We had an issue similar to the chlorine contact diversion when we installed the new return activated sludge splitter box,” says Holder. “We had to either plug the line or pump around it in order to give the contractor a 6-hour window with no return flow.” Again, the staff took advantage of the nighttime low-flow period, took one clarifier out of service, and lowered the level in one of the oxidation ditches, using both basins to contain the RAS.
“We were still filling the clarifiers when the installation was finished,” Holder says. “We were daring the bugs to die. We’re either great operators or the plant is very forgiving. It’s probably a little of both.”
Close work with the contractor led to another solution with old anaerobic digesters, which hadn’t been used for years. As the vessels were being pumped out so they could be converted to coarse-bubble aerobic units, workers discovered more solids than expected, and an abnormally high ammonia content in the remaining water.
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The plant could only process a certain amount of the contaminated water without violating its permit, “so we worked out a plan with the contractor to pump the water out very slowly so it could be treated,” Holder says. “It was a compromise. They were able to put their people to work on other projects while we drained the digesters.”
In the dewatering building, the Middle Oconee plant staff had been having trouble with both the centrifuges and the polymer addition system as the plant modifications began. Construction only exacerbated conditions, and the buildup of solids became worrisome.
“It was frustrating,” says Holder. “Our solids were twice what they should be.” The solution lay in switching polymers. That stopped polymer plugging, and less polymer was required, saving significant money.
“We had to test the new polymer in order to convince management that the change was necessary,” Holder says. “We tried it out and it worked great. In fact, we now think we can get by without thickening in the future.”
Finally, taking one chlorine contact chamber out of service raised additional issues. “Our detention time was essentially cut in half,” says Holder. “We’ve had to experiment, learn new chlorine dosing rates, and rethink the chlorine residual to achieve our fecal kill in less contact time.” The team used no specific calculation, but increased chlorine dosage by trial and error, closely monitoring fecal kill.
“At first we weren’t getting the kill we wanted, so we started adding chlorine at the final clarifier, essentially splitting the chlorine feed between the clarifier and the contact chamber,” Holder says. The fecals have come down, and the plant is using less chlorine than before. The dechlorination process has required adjustment, too. The staff adds sulfur dioxide based on the chlorine residual, resulting in effluent chlorine less than 0.05 mg/l.
Even though the Middle Oconee staff has learned a lot during construction, Bloyer and Holder make sure all operators are fully trained in the new plant processes. They want the training program to result in a library of training materials they will maintain on site.
“Each process manufacturer must provide adequate training on all new pieces of equipment,” Bloyer says. “That’s part of the contract.” The training is to be provided by a technical (not sales) representative from the manufacturer. Training materials must include videos, lessons and tests. “We’re going to get some excellent training,” Holder says.
Bloyer wants the training to qualify for continuing education units (CEUs) that operators can accumulate toward certification. “The goal is to have a library of training here so new employees will get the same training the existing staff received,” Holder says. “We are also contemplating making the training materials available to other municipalities in the area.”
The materials might also come in handy in the plant’s close relationship with the University of Georgia, whose athletic fields are just down the road. “The university frequently uses us for research projects,” says Bloyer. “In the past, they have brought portable labs to the plant and conducted wastewater research.”
Holder says the new treatment facilities throughout Athens-Clarke County might create enough interest that students will want to intern there. “Dave and I are working on that through the ecology department at the university,” he says. “We hope we’ll get some students interested.”
If and when they come, they’ll see the results of good planning, carried out by parties that communicated constantly and trusted each other. Holder “can’t say enough about the level of respect” between the plant management, staff and contractors.
Regular meetings, and even more so, daily one-on-one contact between the plant and contractor, made for a successful project, even in the face of some tough situations. He adds that superintendent Roberts has shown tremendous support and has encouraged the good relationships. “Having the confidence of someone like Mark, with 37 years of experience, is very humbling to say the least,” Holder says.
“We’ve had very few surprises. Just a few nicks, a cut phone line, but nothing serious. I’m proud of our operators. We’d all sit down and discuss a plan, shoot holes in it, and in the end each person knew exactly what they had to do.”
Trust has been the key, both Holder and Bloyer, believe. “Even with my new pickup truck,” says Holder, “if they’re digging a line right next to it, I don’t worry.”
- UV Disinfection (76)
- Chlorination/Dechlorination Equipment (10)
- Phosphorous Removal (10)
- Coarse Bubble Aeration (2)
- SCADA Systems (54)
- Dewatering (11)
- Polymers (8)
- Alfa Laval, Inc. (12)
- Andritz Separation, Inc. (26)
- Hydro International (10)
- JWC Environmental (19)
- Siemens Water Technologies Corp. (68)
- Transdyn, Inc. (1)
- TrojanUV (42)
- Weir Specialty Pumps / WEMCO Pump (13)
- Western Summit (1)
- Submersible Pumps (16)
- Band Screens (4)
- Grit Handling/Removal/Hauling (43)
- Oxidation Ditches (13)
- Centrifuges/Separators (34)
- System Integrator (3)