The Yellow Springs Team Finds The Funds And Makes The Improvements To Meet Strict Phosphorus Limits

The Yellow Springs team finds the funds and makes the improvements to produce quality effluent, meet strict phosphorus limits and handle peak flows.
The Yellow Springs Team Finds The Funds And Makes The Improvements To Meet Strict Phosphorus Limits
Joe Bates, water and wastewater superintendent, shown near the plant’s aeration basin.

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When Joe Bates became superintendent of the Yellow Springs (Ohio) Water Reclamation Facility eight years ago, he knew he had a lot of work to do. And he knew it couldn’t be done for free.

“There was a lot of deferred maintenance here,” he recalls.  “The attitude was, ‘If you can rig up something to keep it running, do it. But don’t spend any money.’ They were penny pinching.

“The village had signed an agreement with the EPA to upgrade treatment, and we were going to have to spend money to get the plant up to speed.  But I also knew there were no funds for construction.”

That’s when he put his ingenuity to work and helped the community, located about 15 miles east of Dayton and home to Antioch College, secure $750,000 through the American Recovery and Reinvestment Act of 2009 (federal stimulus) and nearly $1.13 million in grants from the Ohio Public Works Commission.

He also persuaded city fathers to reserve some of the village’s borrowing capacity for wastewater treatment plant improvements. “Yellow Springs is a tourist attraction, so a lot of our money normally goes into roads and other civic improvements,” Bates says.

The investment totaled $3 million, and because of it the plant is much improved, color coded with Bates’ creative building painting scheme. The facility has also been recognized multiple times for safety.

Flow through

The treatment facility employs a biological phosphorus removal system and disinfection to create high-quality effluent that flows to Yellow Springs Creek and eventually to the Little Miami River, part of the National Scenic Rivers network. Design flow is 0.6 mgd.

At the top of the plant, a 6 mm Headworks International bar screen removes rags and debris ahead of a vortex grit removal system, supplied by WesTech Engineering (WEMCO grit pumps supplied by Weir Specialty Pumps).

Wastewater then passes through a Parshall flume to the biological system, configured for phosphorus removal.

“We have to meet a phosphorus requirement of 1.0 mg/L during the summer months,” Bates says. “In winter, we sample and test but don’t have a requirement that we must meet.” The bio-P process consists of nine tanks that make up five stages of treatment.

In the first stage, return activated sludge combines with raw influent. That is followed by three covered anaerobic stages. An open aerobic zone concludes the series. Submersible mixers (WILO USA) blend contents in the anaerobic stages. The aerated stage employs submersible mixers (also WILO) and fine-bubble aeration (three Hoffman & Lamson blowers, WYSS Flex-A-Tube diffusers from Parkson Corp.). Control of the air supply is based on oxidation reduction potential.

“If we can maintain a consistent mixed liquor, that gives us the most consistent treatment when it comes to phosphorus removal,” says Bates. “That’s our biggest challenge. We don’t like to use ferric chloride to aid phosphorus removal because it’s expensive and the plant can get addicted to it. It’s really just a last resort to meet permit if we have to use it.”

A series of gates enables his staff to manipulate flow, especially to protect the process during high flows that result from significant inflow and infiltration in the collections system. “We can direct flows to the second stage or bypass the second stage and go directly to aeration when we have a highly diluted storm flow in the latter stages of a rain event,” says Bates.

Two 50-foot-diameter, 20-foot-deep Envirex circular clarifiers (Evoqua Water Technologies) accept the treated water, which is then disinfected with chlorine gas, dechlorinated with sodium thiosulfate and discharged. Bates likes the way the plant operates and has effluent numbers to back him up: TSS, BOD and ammonia are regularly below detectable limits. But it wasn’t always this way.

Working better

Bates ticks off a list of improvements that were necessary to bring the plant to its current level of excellence, starting right up front. “The headworks were in the cheapest building I’ve ever seen, with just enough heat in it to keep things from freezing,” Bates says.

The bar screen and grit removal system were essentially exposed to the atmosphere, suffered regular breakdowns and were near the end of their useful life, he reports. “Plus, the grit removal system was not compatible with phosphorus removal. It was aerated, and phosphorus removal requires anaerobic conditions as much as possible.” Bates oversaw the construction of a modern concrete block building with enough heat and controls to house the new bar screen and cyclonic grit removal and classifier apparatus.

Another problem was I&I. Bates recalls one day when the plant flow surpassed 6.5 mgd because of stormwater. Anything above 2 mgd was simply bypassed directly to chlorination, sending diluted, chlorinated sewage to the creek. That, along with the need for phosphorus removal, drove new permit requirements.

An equalization basin has been the answer. “During high flows we can divert up to 2.5 million gallons to the EQ tank for storage,” says Bates. “The plant can handle 4 mgd.” The EQ tank capacity is based on the 6.5 mgd spike recorded a few years back. “We looked at the highest number we could push through,” says Bates.

Yellow Springs is paying attention to the weaknesses in the collections system, although Bates and his department are not responsible for that. The village is addressing the issues by elevating manholes, conducting smoke tests and disconnecting downspouts and sumps from the sanitary sewer system.

Out with phosphorus

The bio-P system takes the place of an old conventional activated sludge treatment train, and the clarifiers have been modified. “We love these clarifiers because of their depth,” says Bates. “But they shared a single withdrawal line for the return activated sludge.” The plant team added a second parallel line to enable more precise control of the sludge blanket in each clarifier.

“Less than a foot deep works best for us with biological phosphorus removal,” Bates says. “There’s no release of phosphorus below the blanket.” A set of new baffles in the clarifiers has improved overflow water clarity.

Changes continue, and they include a new building to contain chemicals and a switch from sodium bisulfite to less-corrosive sodium thiosulfate for disinfection. “The bisulfite caused a lot of corrosion,” says Bates. “We lost a heater that corroded above the bisulfite storage area.”

The biosolids area has a new 30-square-foot cake storage pad, and operators have begun using polymer and geotextile bags (US Fabrics) to dewater solids, especially in winter. The anaerobically digested solids slurry is pumped into the bags through an injector hose and clear water is filtered out. The cake is stored on the pad until area farm fields are ready for application.

“We use a trailer-mounted belt press dewatering service every four to six months, but the bags require very little up-front expense and give us flexibility in dewatering,” says Bates. “The operators say they like using them, and they give us extra storage capacity in the digesters.”

They also save money. Bates calculates that the bags save $2,500 to $3,000 per batch over the cost of the mobile press.

Handling sidestreams

Sidestream treatment is another upgrade. “The filtrate off the belt press and the supernatant off the digesters contain high concentrations of phosphorus, and they must be treated chemically for phosphorus removal,” says Bates.

The plant maintains two sidestream tanks and fills one tank at a time when the mobile belt press unit is operating. “Then we take a sample and determine the phosphorus concentration,” says Bates. “We use ferric chloride and aerate and settle the contents before we pump the water back into the plant. That way the recycle doesn’t affect the biological process. Having two tanks gives us the cushion to keep the belt press operation running.”

While attending to the deficiencies with the old plant, Bates and Brad Ault and Richard Stockton, licensed water and wastewater operators, have found time to rack up an impressive safety record. For each of the past 10 years the plant has received an Ohio safety certificate, and in 2010 it won the Ohio Safety Award for plants with up to nine employees. In 2013 Yellow Springs won the Water Environment Federation’s George Burke Safety Award for Ohio.

And then there’s the WEF Operator Ingenuity Award for the plant color scheme. “Yellow Springs is a very artsy town, very colorful,” says Bates. “So we decided to paint our buildings different colors.” The more dangerous buildings like gas storage are orange, headworks is red, the administration building is yellow, and the RAS pump room is lavender. A new effluent shed will be green, “to show that we’re a lot greener than before.”

People like the colors: “It makes the plant a lot more cheerful than what people might have perceived it to be like.”   



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