One Step Ahead

A Virginia treatment plant prepares in advance for tighter nutrient standards and uses outreach to win public support for a major process upgrade
One Step Ahead
Larry Tignor, Class 4 operator, adjusts the dividers on a belt filter press from OR-TEC. (Photography by Dianne Saison)

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“Be prepared.” That old Boy Scout motto might well be the watchword at the Tappahannock (Va.) Wastewater Treatment Plant.

In anticipation of new biological nutrient removal standards in the Chesapeake Bay watershed, the plant and town management engaged their designer, lined up funding, hired and trained operators, and educated ratepayers well in advance so as to be ready when the new regulations took effect on Jan. 1, 2011.

“Some places waited, but we didn’t,” says town manager Gayle Belfield. “Our style is to be proactive rather than reactive. We wanted to be at the head of the line.” The new standards call for phosphorus reduction to 0.3 mg/l in the Tappahannock effluent, and total nitrogen of no more than 4.0 mg/l. These are significantly tighter than the standards the plant had to meet previously and are in response to a federal and regional effort to reduce pollution of Chesapeake Bay, one of the nation’s most sensitive water bodies (see sidebar).

“Previously, we had a phosphorus standard of 2.0 mg/l, and TKN of 3.0 mg/l,” explains treatment plant supervisor Steve Short. “It’s been a challenge, especially with the cold weather last winter, but we’re getting used to balancing and refining the process to meet our waste load allocations.”

Major upgrade

Before the upgrade, the Tappahannock plant operated as an extended aeration facility, meeting secondary treatment requirements. The new 0.8 mgd (design) plant, designed by Wiley and Wilson, town engineering consultant for more than 30 years, called for a four-stage Bardenpho biological nutrient removal system, installed in the existing oxidation ditches.

“We could have participated in nutrient credit trading to meet our new permit,” says Belfield, “but through the foresight of our town council we chose to secure funds and upgrade treatment. We’re pleased with that decision to be ahead of the game.”

In the Bardenpho process, the first zone provides anoxic treatment, while the second zone is oxic. Nitrates are returned from the second zone to the first. Anoxic treatment occurs again in the third zone, and nitrogen gas is stripped to the atmosphere in zone four. Zones two through four occupy the earlier oxidation ditches. A new basin was constructed for zone one, and flow from it was split between the two trains.

New blowers (The Spencer Turbine Co.) and existing Gardner Denver blowers drive the aeration systems. The four existing secondary clarifiers remained in service. Other improvements included a new Huber mechanical step screen — a unique design with plates rotating on an oscillating cam and lifting solids up steps to disposal. The screen does not operate continuously, but saves energy by activating only when water level rises.

Tappahannock also incorporates alum addition for coagulating phosphorus and uses deep-bed Severn Trent sand filters to remove solids and associated phosphorus from the effluent.

TrojanUV units disinfect the effluent before discharge to Hoskins Creek, which flows to the Rappahannock River and ultimately to Chesapeake Bay.

Rob Mangrum, vice president and project manager for Wiley and Wilson, explains that the deep-bed filters were the choice because they can be used for nitrate polishing in the future. Also, a weir system replaced the existing controller gates ahead of the UV units to assure constant flow during periods when the filters backwash and plant flow is interrupted.

Biosolids are digested aerobically, then dewatered on an OR-TEC belt filter press and landfilled. Short and his team took advantage of the upgrade project to double the digester capacity to 440,000 gallons, and to add a second belt to the press. That has increased the solids content of the pressed cake from 11 to 18 percent, reducing the amount of material landfilled.

The new plant uses Gorman-Rupp pumps throughout. Systems East Inc. supplied the SCADA system, and the plant uses Teledyne Isco samplers and Hach instruments for dissolved oxygen and ORP monitoring.

On-site training

The construction project proceeded in phases to assure continuous operation and permit compliance. The existing biological process consisted of two parallel treatment trains, so as one was converted to the Bardenpho process, the other continued to operate. That sequence also provided a unique training opportunity for Tappahannock’s staff.

In anticipation of the new process and treatment requirements, the town council approved and funded three new operator positions before the new plant went online. Newcomers and existing staff learned about the Bardenpho process as it was installed in 2009. “It enabled us to really learn the process before it went into full operation,” says Short. “Nothing beats on-site training. As you work with the process on a daily basis, you get a lot of practical knowledge.”

Representatives of the various equipment manufacturers were on hand for several days to provide additional training, and plant staff worked closely with Wiley and Wilson to make sure everyone understood the new processes. “It was a real team effort,” says Belfield. “We’ve always worked well together, with lots of give and take.”

Mangrum credits the plant for staying current on technology and trends in the wastewater field. “It’s fun working with them,” he says. “They have a great set of operators, and they really take their profession to heart. This is a very clean, well-organized plant.”

Getting certified

Short and assistant plant supervisor Frankie Sanders also made sure new hires got certified. All operators are certified at Class 1, 2, 3 or 4, even though some came on the job as recently as 2009. “We’ve always stressed certification within our organization,” says Sanders.

Besides Short and Sanders (both Class 1), the staff includes senior operator Lance Franklin (Class 1); operators Adam Townsend (Class 2), Chris Eckles (Class 3) and Larry Tignor (Class 4); facilities manager Steve Davis; pump technician Mike Patterson; and fleet maintenance specialist Johnny Davis.

The Virginia Department of Environmental Quality (DEQ) requires operators to acquire a specified number of Continued Professional Education contact hours during each two-year certification renewal period. Classes are offered through the Virginia Rural Water Association, and through the DEQ and other sources. On-site training is available.

“Each operator at our plant is required to attend a number of contact hours of classroom training each year to meet the requirement,” says Short. “The town also supplies each operator trainee with correspondence courses purchased through California State University Sacramento.”

The emphasis on certification and training has proven worthwhile. The new nutrient requirements took effect in the middle of one of the coldest winters on record along the East Coast. “The cold weather has definitely been a challenge,” says Short. “Our nitrification-denitrification definitely slowed down in the winter. We had water temperatures of around 8 to 9 degrees C, and if we have anything below 15 degrees C, we start to worry.”

Oxygen levels are the key, of course, and Short and Sanders credit the Hach instrumentation for helping the plant maintain adequate dissolved oxygen levels throughout the process steps. A non-rated glycerin chemical can be added to the fourth zone to help feed the biological organisms in cold weather.

“By January (when the new limits took effect) we were starting to see good numbers,” Short observes. The plant’s new allocation is just 731 pounds of phosphorus and 9,761 pounds of total nitrogen per year.

Cost justification

While Tappahannock ratepayers are seeing higher sewer charges, the capital cost of the upgrade project was entirely borne by state funds. The total cost of $8 million came out of the State of Virginia revolving loan fund, and through a water-quality improvement grant.

Again, the town took a proactive approach to the financial portion of the project. As the necessity to upgrade treatment became apparent, Belfield did a thorough rate structure analysis of all surrounding communities. The numbers helped justify the Tappahannock rate increase and also provided a reasonable estimate of the impact on treatment costs for the next several years. “It’s an estimate, but it helps us compare our actuals to our projected expenses,” Belfield says.

The town also engaged in a consistent program of public education, cooperating with the local newspaper in a series of articles about the need for the upgrade and the approaching cost increases. “We reported what we were doing and where we were going,” Belfield says.

He acknowledges that additional treatment costs and increased rates can be painful. “We realized we were going to have to extend hours of operation in order to meet the new regulations,” he says. “But we started the budget preparations early, again being proactive. Our governing body was receptive, and when we had public meetings on the project, there were no objections.”

The Tappahannock staff does its part by looking for ways to save on operating costs. “The double belt press enables us to handle an increased solids load but send less volume to the landfill,” says Short. That’s a saving, as is the potential for operating just one side of the biological process when conditions permit. “We’re really two treatment plants here,” says Short. “If we can get by running just one train, that’s more economical.”

The Tappahannock staff performs its own maintenance wherever possible. “If we can do it ourselves and not have to send it out, that’s going to save us money,” Short says.

Pride of ownership

It’s not often that municipal leaders visit their wastewater treatment plants, but in Tappahannock, town manager Belfield stops by every day. And it’s not just for coffee, although he admits the brew is pretty good there. “When I came to the town in 1976, I was a sewer and water inspector for a newly annexed area,” he says. “It’s a whole lot easier to talk with the operators when you know what they’re talking about.”

Mangrum says Belfield is very hands-on and “really knows what makes sense at the plant. That’s a good thing.” Belfield’s visits exemplify what he calls “total town involvement” in the new treatment facilities. “We’re proud of what we’ve done here,” he says. “The council and the public are behind our efforts. That’s the most important piece of infrastructure we have.”


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