Too Much Rain Leads to Upgrades for Vermont WWTP

The Enosburg Falls team acts to limit overflows from wet-weather events and lays aside funds to make regular plant process improvements.
Too Much Rain Leads to Upgrades for Vermont WWTP
Brian Ovitt adjusts the double disc pump (Penn Valley Pump).

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Rainy days used to spell trouble for the Enosburg Falls (Vermont) Wastewater Treatment Facility in the form of combined sewer overflows. That led to a major upgrade in 2012, including a 30,000-gallon offline storage tank to contain excess flows for later treatment.

Meanwhile, Rodney Allen, chief operator, with assistant Brian Ovitt, created a rainy day fund to make repairs and replacements that keep the day-to-day operations running smoothly. The fund is supported by sewer allocation fees and a $10,000 annual operating budget set-aside. “We identify projects and make needed improvements every year,” he says. “This year we’ll install a new drive mechanism for the anaerobic selector tank mixers and replace one of our pumps.”

Out with CSOs

The Enosburg Falls facility dates to 1977, when it replaced septic tanks that risked leakage to Vermont’s Missisquoi River, a tributary to Lake Champlain and the plant’s receiving stream. Designed by the DuBois & King engineering firm, the plant included headworks, extended aeration activated sludge treatment, clarification and chlorine disinfection.

The village began separating storm sewers and roof drains from the sanitary sewer system in 1995. Phosphorus reduction programs were completed in 1995-96 with the addition of an anaerobic selector process for biological phosphorus removal. The aeration systems were upgraded in 2005 with fine-bubble diffusers (Sanitaire - a Xylem Brand).

The 2012 upgrade responded to a state order to control CSOs and included the 30,000-gallon cast-in-place concrete tank to store excess influent when rainfall exceeded 2.5 inches in 24 hours. Since then the village has had no CSO violations. “It has been needed on a few occasions but has always performed to design,” Allen says.

During the same upgrade, the village installed a new influent screening structure and grit removal system, added another chlorine contact tank, and installed a double disc pump (Penn Valley Pump Co.) to drain that and other tanks as needed. The work also included improvements to the blowers, including variable-frequency drives for the existing aeration systems. Design engineer was Aldrich + Elliott, and NECCO was the general contractor.

Effective bio-P

Today, the plant handles an average flow of 250,000 gpd. Wastewater first passes through an influent structure that includes two coarse bar racks for screening. The headworks includes a vortex grit removal system with grit collector, grit pumps and grit cyclone (all from Envirodyne Systems).

The anaerobic selector tanks, funded entirely by a state grant, provide conditions to enhance biological phosphorus removal. The contents are maintained at zero dissolved oxygen and are mixed by Flygt - a Xylem Brand, Sulzer Pumps Solutions and Hydromatic submersible mixers. Retention time is about two hours. Although the plant has capability to add alum for phosphorus precipitation, that is seldom used.

“We piloted the selector system back around 1999-2000,” says Allen. “We proved to the state that we could operate it and biologically remove phosphorus.” After biological treatment, the flow passes to the aeration basins and on into dual rectangular clarifiers. The effluent is then chlorinated and flows through two contact tanks that provide about four hours’ detention time.

Biosolids are aerobically digested, again using fine-bubble aerators. The liquid material at about 3 percent solids is hauled by a contractor to the Plattsburgh (New York) Wastewater Treatment Plant about an hour away for dewatering followed by landfilling or composting.

Ready source of funds

The rainy day fund has performed well. Allen calls it his sewer equipment replacement fund. At present, the fund totals about $260,000, not a big number to midsized and large wastewater authorities, but a goodly sum for a plant as small as Enosburg Falls.

“Every year we make a list of in-house projects that need doing.” Allen says. “This year, we’ll put new vertical-shaft drives on the mixers in our selector tank. We’ll assist in the installation and hope to achieve better mixing, greater efficiency and easier access for maintenance. Allen and Ovitt also installed a new replacement pump (Gorman-Rupp Company) at one lift station and will widen the plant’s access gate to allow large vehicles like biosolids trucks to enter and leave more easily. All these projects will cost an estimated $30,000.

“We don’t need big money for these projects,” says Allen. “Every year, we keep the plant looking good and working well. We set this fund up when I first started working here. The state liked it. It’s worked out really well for us. We know how long things will last; we don’t wait for them to fail. We’re refurbishing the plant for the future.”

Strong staff

The do-it-yourself approach is not surprising at Enosburg Falls. Allen and Ovitt are combat veterans, and answering the call is nothing new to them. Allen, who started as an assistant at the plant in 1978, served in Vietnam, where he was a mess hall sergeant for three years. Ovitt, who has a degree in environmental and civil engineering, served in the U.S. Army from 1989-95 as part of an air assault unit.

The two staff the plant each weekday, then alternate on-call duties on weekends and holidays, including three-hour shifts on Saturdays and Sundays. They use beepers and smartphones to maintain contact during off-hours.

Computer-driven data and manual recordkeeping enable Allen and Ovitt to keep track of maintenance requirements. “We keep a record on every piece of equipment in the plant,” says Allen. “We update it every month. We keep a regular book. If something goes down, we have a backup. Good recordkeeping over the years has allowed us to plan for the future.”

Staying safe

The plant maintains an excellent safety program. “We have regular safety meetings,” says Ovitt, who has completed OSHA safety training. The Vermont Rural Water Association provides additional safety training.

“With a small operation like this, we have a lot of responsibilities, including process control of the plant, state reports, maintenance, lab analysis, outside sewer lines and pump stations,” says Allen. “We’re also involved in the annual budget process and sewer allocations. But it works out well for us. We’re cross-trained in everything. We keep the ball rolling.”

In the nomination for Enosburg Falls’ 2016 Plant Excellence Award from the Green Mountain Water Environment Association, the reviewer complimented the operators for their dedication and proactive approach: “They have an excellent preventive maintenance program and are innovative and mechanically skilled. They take great pride in their work.”

The plant has an excellent compliance record. BOD removal is 99 percent, and TSS removal is 96 percent. Effluent phosphorus is typically about 0.2 mg/L, well within the permit. With the treatment provided, the effluent is crystal clear and nearly free of pollutants. Rain or shine.

Plaques aplenty

The Enosburg Falls Wastewater Facility and its staff members have earned several major awards for excellence. They include:

  • Plant Excellence Award, Green Mountain Water Environment Association — second place, 1981-83; first place, 1984, 1987, 1990, 2016
  • Rodney Allen, Operator of the Year, New England WEA, 1991; Outstanding Service in Water Pollution Control, Green Mountain WEA, 2010
  • Brian Ovitt, Andrew D. Fish Laboratory Excellence, Green Mountain WEA, 2015

Allen notes that the awards in the 1980s were received when the late Sam Gates was chief operator: “He set a high standard for operation and commitment that is evidenced in the staff today. All employees past and present have taken great pride in operating this plant and receive support from all other departments as well as local government.”


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