Virginia plant raises the bar with innovative wastewater management program, leading to numerous operational excellence awards
Operators at the Noman M. Cole Jr. Pollution Control Plant are deep thinkers. They ask: What could go wrong? And how will we handle it?
“We do a lot of monitoring upstream so we can troubleshoot issues and make process adjustments in real time,” says Mike McGrath, manager of the plant in Fairfax, Virginia.
“For example, we used to depend on day-old lab tests on the final effluent to monitor ammonia. Now we field-test upstream at the activated sludge tanks twice during each shift.”
They also monitor phosphorus, sampled upstream of the outfall. “We shoot for 0.1 mg/L, so if we see numbers above 0.5 mg/L, we know we will have trouble upstream,” McGrath says. The approach has worked out well. The facility has received the National Association of Clean Water Agencies (NACWA) Peak Performance Award for 30 consecutive years.
The plant is part of the Fairfax County Wastewater Management Program, a division of the county Department of Public Works and Environmental Services. The 67 mgd plant treats about 40 percent of the 100 mgd of wastewater generated in the county. It is staffed with 48 operators (four shifts of 12) and 14 lab technicians.
To help preserve local water resources and reduce nutrient discharges, the plant reclaims 400 million gallons per year for sale to customers that include a waste-to-energy facility and the Fairfax County Park Authority. The plant uses 2 to 3 mgd of reclaimed water for chemical makeup, seal water and scrubbers. The wastewater program was named a Utility of the Future Today by a partnership of water organizations that includes NACWA, the Water Environment Federation, the Water Environment & Reuse Foundation, and the WateReuse Association, with input from the U.S. EPA.
Effluent discharged to Pohick Bay typically contains 2 mg/L CBOD5, 1.15 mg/L TSS, 0.06 mg/L total phosphorus, 0.1 mg/L ammonia nitrogen, and 1.9 mg/L total nitrogen.
Eligibility for the Platinum Award is based on testing 365 daily, 52 weekly and 12 monthly effluent sample results. The operators perform field tests on ammonia, total phosphorus, settling, spins (sludge concentration analysis), chlorine residual, pH, dissolved oxygen and turbidity. Parameters subject to upstream testing with online analyzers include phosphorus, nitrogen, ammonia, BOD, TSS and pH.
The team meets at 3 p.m. every day to review existing challenges and to plan the night shift and next day’s activities. “Making permit is ingrained in everyone, and our supervisors have a lot of latitude and freedom in making decisions on the fly,” says McGrath. “Our operations staff size allows us to do more troubleshooting and optimization.”
Recent upgrades have boosted the plant’s success. In 2013, to help meet nitrogen and phosphorus limits, the county began methanol addition in the biological nutrient removal process, which is configured for nitrification and denitrification. The plant also added moving-bed bioreactors (MBBRs) for tertiary nitrogen removal and a reuse water distribution system.
Raw sewage passes through bar screens (Vulcan) and is pumped to the primary clarifiers (Evoqua Water Technologies). The flow then enters the activated sludge tanks, followed by the secondary clarifiers. From there, it flows to the tertiary treatment system: Kruger MBBR biological treatment, carbon addition, clarification and coagulant addition.
The chemical sludge is returned to the head of the plant to improve upstream treatment. The flow continues to multimedia filters (Leopold - a Xylem Brand), followed by sodium hypochlorite disinfection. The final effluent is dechlorinated with sodium bisulfite and discharged to Pohick Creek. Biosolids are dewatered with centrifuges (Alfa Laval Ashbrook Simon-Hartley) and then undergo thermal oxidation in multiple-hearth incinerators before being landfilled. Natural gas from the landfill fires the afterburners on the incinerators, reducing facility greenhouse gas emissions by 60 percent.
A SCADA system with GE Intellution HMI and Allen-Bradley PLC’s with ControlLogix software (Rockwell Automation) allow monitoring of the entire plant. “The system monitors 25,000 points and includes more than 50 PLCs, 22 work stations and 10 servers,” says McGrath.
Many of the operators have been with the county for more than 10 years, and some for more than 26 years. “They know they’re going to be retiring at some point, and are very generous in sharing their knowledge,” says McGrath. “So there’s a lot of unintentional, or informal, learning going on by the newer operators.”
They also receive more formal training. “In the old days, the staff would learn by looking over another operator’s shoulder, but they might not learn everything,” says McGrath. “So now we have more structured training and a competency checklist at each duty station with a list of things people need to know to operate the plant.”
The county helps operators maintain their certification. For uncertified employees who are hired, “We provide training and materials so they can get their Class 1 operator’s license, which is the highest state certification level.” Training on new equipment is provided by vendors and consulting engineers, but McGrath schedules more training after the operators have worked with the equipment for a while.
Plant staff members are organized into administration, operations, laboratory and maintenance. “Because of the plant’s size and county human resources requirements for class specifications, the wastewater professionals here are more specialized than in some other treatment plants,” says McGrath.
Operators’ main duties are process monitoring, adjustment and troubleshooting, sample collection and some laboratory testing, data collection, general housekeeping, and assisting in startup and fine-tuning of new facilities. They also place facilities in and out of service as needed for process, maintenance and construction requirements.
McGrath has been with the plant for 14 years. Key operations staff members include:
- Trevor Austin, operations superintendent (19 years)
- Gulshan Gupta (14 years), Mark Makuta (26 years), Clinton Davis (26 years), Ronald Davis (27 years), operations supervisors
- Roger Silverio, operator in charge (27 years)
- Mike Rynders (14 years) and Roger Bailey (26 years), operations specialists
- John Allen, lab quality control manager (11 years)
The team often goes above and beyond to solve problems. “One of the most memorable times was during Tropical Storm Lee in September 2011,” says McGrath. “The town received over 7 inches of rain in three hours, which according to NOAA was off the charts, above a 1,000-year rainfall.”
The plant fully treated all the wastewater during the first night (Thursday). Some flow was stored and treated the next day. “Some disinfected secondary treated liquid spilled out of a tank,” McGrath says. “The operators, some staying over from a previous shift, sandbagged the tank to prevent it from being worse.”
The storm flooded an empty storage pond and a number of basements and tunnels. The high-water mark for the flood was shoulder high in the basement of the incinerator building.
“Staff and contractors dewatered these spaces and did some clever work to dry out motors overnight and get equipment delivered on Saturday,” McGrath recalls. “The work was well coordinated with different shops working together to attack problems simultaneously. Amazingly, maintenance turned over the incinerator to operations to start warming up by Saturday night.”
One of the plant’s goals is to increase efficiency. “We feel like we get very good performance relative to our permit requirements, but we challenge ourselves to perform just as well with fewer resources, such as chemicals, electricity and budget,” McGrath says.
Phosphorus removal is one example. Since 1978, the phosphorus permit limit has been 0.18 mg/L. The plant started with two-stage lime treatment but switched to multipoint ferric chloride addition within a few years. “In 1990, our ferric chloride dose was around 25 mg/L,” McGrath says. “Since then, we’ve tried numerous ways of reducing that by using ferrous sulfate or alum, or using different feed point combinations and tertiary clarifier recycles for dosing the head of the plant.”
They have had some success with biological phosphorus removal in the secondary process: “Operator attention becomes really important because we are operating much closer to the edge — just enough to meet limits, but not too much that chemicals are wasted. Lately, we’ve been able to achieve our performance with a ferric chloride dose of about 10 mg/L.”
Perhaps the biggest challenge is operating the incineration system. “Not only must we achieve permit limits, but we must document that we are operating according to best combustion practices,” says McGrath. That includes hourly operating ranges, daily instrumentation calibrations, maintenance, training and emissions monitoring.
Recent regulations (Sewage Sludge Incineration Maximum Achievable Control Technology, or SSI MACT) have increased compliance complexity: “For the operators, this means additional data collection, testing and reporting requirements, and more stringent operating parameters, increased operator training and certification.”
Tank rehabilitation poses another challenge. “During rehabilitation construction, some tanks are unavailable, so we have to be much quicker about responding to problems on the remaining tanks. This puts a lot of stress on our operations and maintenance crews. When the rehabilitated tanks are returned, there is extra troubleshooting as we work out the glitches.”
The plant team is planning some major upgrades, including a switch to UV disinfection within four years, and a biosolids improvement program. “The biosolids program will rehabilitate existing multiple-hearth incineration air pollution control equipment to meet MACT regulatory standards,” says McGrath. “It will also rehabilitate all solids process infrastructure to operate for the next 15 years or so.” Those processes include gravity thickening, dissolved air flotation thickening, storage, and centrifuge dewatering. The first phase is to be completed in 2017, and the last phase in about six years.
The county would also like to generate electricity from biosolids: “As part of our biosolids rehabilitation program, we’re designing an energy recovery system to use on our multiple-hearth incinerators.” The county would also like to find more customers for its reclaimed water and a beneficial use for its incinerator ash.
For now, the plant is in great shape to keep doing what it does best: meeting permit for the benefit of its 380,000 customers. The plant’s 130 staff members deserve all the credit, says Judy Fincham, outreach coordinator: “We are like an extended family. Everyone takes ownership, and to me that’s key.”
McGrath agrees: “It’s all about teamwork. If someone needs help, the others will step up. I’m proud of this group.”
The operations staff members at the Noman M. Cole Jr. Pollution Control Plant give back by donating time to help students learn about water quality under the Sewer Science program.
Says Judy Fincham, outreach coordinator, “This national hands-on laboratory program was introduced to Fairfax County high schools in 2006, and so far it has trained more than 17,500 students and 70 teachers on the importance of water quality, how wastewater is treated, and the scientific principles that apply.”
During two 90-minute classes in high school science classrooms, students learn about primary clarification, biological secondary treatment, disinfection, filtration and ammonia reduction. “They get to produce simulated wastewater, take the water through the treatment processes, and test for pH, ammonia, turbidity and chemical oxygen demand,” Fincham says. Materials, supplies, and student and teacher workbooks are provided by Fairfax County.
Plant operators volunteer as mentors, assisting the teachers in the classrooms. “They are very comfortable in this role because they are basically explaining what they do in their daily jobs,” says Fincham. Plant staff members also help high school students with their water quality science projects. Laboratory personnel provide mentoring and space to work in the plant lab. Some recent projects have won state awards.
Educational outreach is a great way to encourage students to choose clean-water professions once they graduate, says Fincham: “We developed a pilot program with a local high school to recruit recent graduates for hard-to-fill positions. We’ve hired three full-time operators through that program.”