In Mecklenburg County, plant personnel collaborate on biosolids management. The results and the awards show that the approach is working.
Working at the McAlpine Creek wastewater treatment plant means working as a team — not just within the plant, but among all the plants operated by Charlotte-Mecklenburg Utilities.
The McAlpine Creek plant is one of five treatment plants operated by Char-Meck, which serves the City of Charlotte, N.C., and surrounding Mecklenburg County. The plants treat a total of 123 mgd.
The utility emphasizes working together through a variety of programs and has seen the results. Operators readily share information within and between plants. Operators from the liquid and solids sides have a better understanding of their relationship. And awards keep coming in.
The utility’s wastewater treatment plants — McAlpine Creek, Sugar Creek, McDowell Creek, Mallard Creek and Irwin Creek — have their own wastewater treatment systems and solids handling equipment (belt filter presses and centrifuges). The one exception is Sugar Creek, which pumps its solids 7.5 miles to the McAlpine Creek plant. Ultimately, contractor Synagro Technologies Inc. transports the biosolids for land application at farms in North Carolina (10,500 acres) and South Carolina (3,400 acres).
The whole process runs on a combination of technical know-how and cooperation.
Each on its own
At 64 mgd (design), the McAlpine Creek plant is by far the largest. It is also the only plant that treats solids and overflow wastewater from another facility (Sugar Creek). Built in 1996, McAlpine Creek has been upgraded seven times, most recently in 2000.
Treatment includes biological nutrient removal for phosphorus, followed by sand filtration and dosing with sodium hypochlorite for disinfection and sodium bisulfate for dechlorination. The plant staff includes Grade 4 operator Ritchie Crump, equipment operators Jack White and Larry McKinney, plant mechanic Ned Seaman, plant supervisor Kim Neely (Grade 4), and chief operator Keith Purgason (Grade 4).
After primary treatment at McAlpine, de-gritted flow is split to the north and south trains, each providing primary sedimentation, activated sludge treatment, and secondary clarification.
The most recent expansion added two 8-inch sludge lines connecting the Sugar Creek and McAlpine Creek plants. These lines, one for primary and one for waste activated sludge, enabled decommissioning of sludge drying beds at Sugar Creek that were having odor problems.
Primary sludge from McAlpine Creek and Sugar Creek is thickened in two 45-foot-diameter gravity thickeners. Waste activated sludge is thickened in three centrifuges to 5 percent solids. The two streams combine in eight anaerobic digesters. After digestion, the solids are stored in two 1-million-gallon tanks before dewatering. Three Alfa Laval centrifuges then dewater the material to 20 percent solids.
The plants’ treatment processes vary. Sugar Creek (20 mgd design) uses activated sludge. Irwin Creek (15 mgd) uses trickling filters along with activated sludge. Mallard Creek (12 mgd) is an activated sludge facility with reclamation. McDowell Creek (12 mgd) has biological nitrogen removal.
Solids treatment processes also differ. Irwin Creek uses anaerobic digesters and leases a skid-mounted belt filter press. New dewatering equipment will be installed as part of future upgrades. McDowell Creek uses anaerobic digesters and two Ashbrook Simon-Hartley belt filter presses. Mallard Creek relies on Bird Humboldt (Andritz Separation Inc.) centrifuges for thickening and dewatering.
A line on the wall or pad
There is a strict line where the biosolids become the responsibility of Synagro. Under the contract, Char-Meck provides a quality product, and Synagro manages storage and delivery.
At McAlpine Creek, a screw conveyor runs from inside the dewatering building to two 500-cubic-yard silos outside. Once solids hit the conveyor, they are Synagro’s responsibility. From the silos, Synagro takes the biosolids straight to a farm for land application, or across a parking lot for storage at the residuals management facility (RMF). The 235,000-square-foot RMF is fully enclosed.
For the other three sites that manage their biosolids, Synagro takes charge as soon as the material drops onto the outside storage pads. These concrete pads are covered and are bordered by short walls. “When the pads reach 50 to 70 percent in capacity, the decision is made to empty the pad and take the solids to a land application site,” says Jackie Jarrell, manager of the environmental management division. Annual solids volumes are:
• McAlpine Creek; 11,310 dry tons per year.
• Mallard Creek; 1,026 dry tons per year.
• McDowell Creek; 1,445 dry tons per year.
• Irwin Creek; 1,572 dry tons per year.
Synagro transports solids to the land application sites, stages them before application, and uses a spreader to disperse the material.
Awards for plants and people
Biosolids management is just one area in which Char-Meck Utilities excels. All five plants received 2008 awards from the National Association of Clean Water Agencies. McDowell Creek received the Platinum award for 100 percent permit compliance over the past five years. Mallard Creek, McAlpine Creek, and Sugar Creek received Gold awards for 100 percent compliance for a full year. Irwin received a Silver award for five or fewer violations in a year.
The agency has received other awards for environmental stewardship education, and for support of employees on active duty with the National Guard.
Char-Meck also helps its people enhance their career skills and move up the ranks. The process starts during the job interview. “When someone applies for an operator’s position, we explain the process,” says Jarrell. “They have six years to reach a Grade 4 level.
“There is support for operators who are going to classes and taking exams. They have two or three chances to pass the exams. The other operators help them because everybody wants everybody else to pass.”
Incentives for passing the tests are more than the satisfaction of a job well done. Operators benefit financially as they move up in grades. “We have a step program,” Jarrell says. “When you move up from Grade 1 to Grade 2 there is an increase in pay. Each grade has more responsibility. It’s a succession plan. We have people who are Grade 4 operators now who will be leaders in our profession. You see it as they develop.”
Education isn’t limited to operators, says Shannon Sypolt, water quality specialist and residuals back-up operator in responsible charge (ORC). He started his career in consulting with only limited experience in wastewater treatment.
“I’m in the administrative group, and I started in the lab, but now I’m a Grade 1 operator and have sat through the Grade 2 classes,” he says. “These classes allow people to move laterally. Without the additional education, I wouldn’t be able to perform at the level I am now.”
Several years ago, Char-Meck launched a competition and optimization program, requiring departments to compete with the private sector for work. Bids were prepared, and when a department beat the private sector, a memorandum of understanding was issued that included the detailed scope of services modeled after the winning bid.
“It used to be that every plant went under optimization independently,” says Jarrell. “But now we put all the plants together. There is one budget for all the plants, so the plants help each other to optimize because it all comes out of the same pot of money. It seems to have helped. Supervisors are helping each other, there’s more teamwork.”
The utility has also seen marked improvement with the implementation of ISO international quality standards, specifically ISO 14001 which addresses environmental management of the utility’s biosolids management program. “Mallard Creek was the first plant to receive certification, now all of the programs are certified,” Jarrell says. “We believe the ISO program will have more impact than the optimization program. ISO gets to all the employees and looks at why each person does what they do.”
As part of the ISO initiative, the utility aims to cross-train a number of treatment plant operators so they know the entire process, rather than just their own jobs. “Most of the operators in the plant are not in dewatering,” says Jarrell. “They pay attention to the liquid side, meeting the NPDES permit. They’re not involved with the digester or dewatering equipment. We want to help them understand the connection and impact of what they do — that if they change something in their process, it affects the solids.
“If the operators change something and more polymer is needed for the solids, then that’s an increased cost. If the solids people can’t get to the required percent solids, then that means more money to Synagro for transportation. The ISO program and training have helped bring attention to the liquid and solids sides of the plant.”
Working together isn’t just good for the plant liquids and solids. It’s good for the people, too. And they have the awards to prove it.