Problem: An Overloaded Treatment Plant. Solution: A New Facility With Water Reuse

Sophisticated processes and an experienced operator team keep a small Virginia facility in compliance with tough permit limits

Problem: An Overloaded Treatment Plant. Solution: A New Facility With Water Reuse

Aerial view of the Zion Crossroads Wastewater Treatment Plant.

It was a case of turning a problem into an opportunity.

The Zion Crossroads Wastewater Treatment Plant was organically and hydraulically overloaded. At the same time, residents of a nearby historical district were concerned about the plant’s discharge going through their community from an old impoundment built years ago for flood control.

The solution? Build a new plant able to produce Class 1 effluent for reuse in golf course irrigation or discharge through a 10.5-mile force main to the South Anna River.

The new plant, in Louisa, Virginia, 20 miles east of Charlottesville, features a five-stage Bardenpho biological nutrient removal process (Ovivo) and Ozonia UV disinfection (SUEZ Water Technologies & Solutions). It went into operation in 2011.

According to Wesley Basore, wastewater operations manager with the Louisa County Water Authority, the effluent meets some of the tightest standards in Virginia due to state-of-the-art processes and the efforts of a proud and capable staff. “We’re one of only five localities under the oversight of the Department of Environmental Quality – Northern Regional Office doing reuse,” he says.

“We were discharging through the Historic Green Springs community, a 10,000-acre district with historical homes. The old plant was not meeting permit, operating at about 120% of our organic capabilities and right at our 100,000-gpd hydraulic design.”

A new look

The new plant has a design capacity of 700,000 gpd and produces high-quality effluent that contributes to the irrigation of the 18-hole golf course at the 626-home Spring Creek development (build-out is 1,200 homes). About 20,000 gpd is still pumped through the pipeline to the river. “It takes 14 days for the water to get to the outfall,” Basore says. “We like to keep water moving in the pipeline to keep it from going stagnant.”

Wastewater is collected from the Spring Creek community and about 58 commercial establishments, including a 1 million-square-foot retail distribution center (dry goods and refrigerated items), which has a pretreatment permit. Contaminants of concern there are zinc and copper. “We’re working with them on that, including bench-scale testing supervised by our engineer, Dewberry of Richmond,” Basore says. “It’s a permitting issue and affects our land application allowance.”

At the plant, wastewater is moved through an on-site pump station to the headworks, which contains a mechanical bar screen and an aerated grit collector. Through a splitter box, the water can be directed to an equalization basin, the BNR process, or both, depending on flow volume.

The BNR process consists of a first-stage anaerobic zone, followed by an anoxic stage, an aerated reactor, a second anoxic stage and final reaeration before the water flows to the secondary clarifiers. At present, the plant operates a single clarifier basin, keeping the other in reserve for maintenance.

From the clarifiers, the flow passes through two AquaDisk cloth media filters (Aqua-Aerobic Systems). Then it’s on to post-aeration, the UV units, reaeration, and discharge to the reuse impoundment or by five-stage effluent pumps (Goulds Water Technology, a Xylem brand) to the pipeline.

“We opted for vertical UV units because it was easier to replace individual bulbs,” Basore says. “With our old horizontal system, if a bulb went out, we’d have to pull the entire rack.”

ABB flowmeters monitor flow rates, and Hach ORP and dissolved oxygen sensors control the reactors. Hach turbidity sensors are installed at the filters as part of the reuse permit. Nitrates are also monitored using Hach sensors for chemical control.

“We adjust chemicals off the nitrate sensors, and the aerator speeds are controlled by the DO sensors,” Basore says. The ORP sensors control the recycle gate and the percentage of recycle that is fed back into the first anoxic zone. A carbon source is fed into the second anoxic zone to minimize nitrate levels. Alum is added at reaeration for phosphorus control.

Redundant systems

“I’ve seen plants the same size as ours with many more sensors,” says Nancy Pugh, chief operator. “Ours have worked beautifully since day one.”

The treatment process features a great deal of redundancy. “We did that to ensure against violations,” Basore says. “Our BNR system has dual aerators, and we have a chlorine system on site as a backup for disinfection. That’s in case we’d have an E. coli outbreak in either the reuse or outfall line.”

In addition, the plant has two final clarifiers and two cloth filters. “We run just one basin because of flow, which averages 150,000 gpd,” Basore says.

The plant operates under a tiered permit in addition to a reuse permit. At 700,000 gpd (design capacity), the requirements are 3.4 mg/L for total nitrogen and 0.4 for total phosphorus, among the strictest in the state. At flows below 311,000 gpd, the limits are 6 mg/L for total nitrogen and 0.6 for total phosphorus. In 2018, the plant average effluent total nitrogen was 2.4 mg/L and total phosphorus was 0.12 mg/L.

Because of the Chesapeake Bay watershed rules, the plant’s limits are locked. Reuse helps because any discharge not flowing to the river doesn’t count toward the plant’s effluent limits.

Solids are digested, then dewatered to about 20% solids on a centrifuge (Andritz), which Basore says was chosen because it produces a small, concentrated side stream. The cake is landfilled, but land application is available as a permitted alternative.

An Allen-Bradley SCADA system (Rockwell Automation) monitors and controls plant functions.

Licensing issues

While meeting tight discharge limits is an ongoing challenge for the Zion Crossroads staff, another pressing issue is in play. “We’re fast approaching an operator shortage,” Basore says. “Maybe we’re already there. Nancy and I are near retirement.”

It’s difficult to find operators who hold a Class 1 license: “Reuse is a driver for advanced operator levels. But operators moving up into the higher classification — that’s not happening.”

It’s more than just studying and passing the tests: “It truly is that some of the test questions deal with things operators have never even heard of. If they don’t pass, they start to question themselves.”

Closed-book testing can lead to as high as 80% failure rates, Basore maintains. “A lot of those questions on best practices are really a matter of one’s individual perspective. The correct answer can be subjective at best. How are other states dealing with this?”

For now, Basore (Class I) has a qualified staff. In addition to Pugh (Class I), Rob Ziolkowski is a Class 2 operator, Harley Brooks is Class 4 and Ryan Amos is a trainee. They rotate through 12-hour shifts during the week and 8-hour shifts on holidays and weekends.

“We all work together,” Basore says. “We have responsibility for water as well as wastewater. Maintenance helps us, and we help maintenance. We’re one big group of people working for a common cause.”

Double winners

It’s great when a water or wastewater utility team member wins a statewide award. It’s even better when two team members are honored.

That was the case last year at the Louisa County Water Authority, where Nancy Pugh, chief operator, and Chris Compton, maintenance manager, won awards from the Virginia Rural Water Association.

Pugh, who has been with the authority for 12 years, was named Wastewater Operator Specialist of the Year. She is responsible for operation of the Zion Crossroads Wastewater Treatment Plant. “This is the third utility I’ve worked for and the smallest,” she says. “I was surprised but pleased to receive the award.”

She isn’t bothered by working in a man’s world: “When I sat for my first license exam, there were about 300 men and four women testing.” She enjoys working in the environmental field. “It’s in my family,” she says. “My dad was an environmentalist. It’s great to have a job doing something I believe in.”

Compton has been with the authority for 16 years. He’s a jack-of-all-trades, handling maintenance for water and wastewater, tending lift stations, reading and installing meters, using a line locator, monitoring new infrastructure and running the water well system, including all Virginia Department of Health water-quality testing.

He is licensed in both water and wastewater and likes the variety: “There’s always something to do. It’s not the same thing every day. The days fly by.” Compton was surprised by the award and honored to attend the state conference for the first time.

“It was great to meet people, share situations and talk with vendors,” he says. “When I started, technology was minimal in the field. Now there has been so much advancement in equipment: I am amazed at just how far it has come in the last decade. This is an ever-growing field, and we’re going to need water forever.”


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