An Iowa Team Masters A New Plant's Biological Nutrient Removal Process

An Iowa plant team adapts quickly to biological nutrient removal in a brand-new advanced treatment facility with a list of awards that should instill community pride.
An Iowa Team Masters A New Plant's Biological Nutrient Removal Process
Team members at the Clinton facility include, from left, Gaylon Pewe, operator; Dan Riney, water quality superintendent; Ken Decker and David Burn, operators; and Bob Milroy, assistant superintendent. (Rotary presses from Fournier Industries.)

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EDITOR’S NOTE: Since this article was written, Clinton’s water quality superintendent Dan Riney has retired from that community and has taken a position with the City of Topeka, Kan.

Nutrient removal is a hot topic in operator circles. There’s worry about stricter nitrogen and phosphorus limits and the cost and difficulty of meeting them.

If you ask Dan Riney and Bob Milroy, the concerns are largely unfounded. They run the new Clinton (Iowa) Regional Water Reclamation Facility and its biological nutrient removal (BNR) process. The BNR added less than $1 million to the plant’s cost. The operations staff adapted easily to it. The process is heavily automated.

Best of all, the plant’s effluent today meets what the Clinton team expects to be its permit standard in 2018: yearly averages of 10 mg/L total nitrogen and 1.0 mg/L total phosphorus. “It’s nothing to be scared of,” says Milroy, assistant plant superintendent. “It’s just more concrete, a few more mixers and a few more mixed liquor pumps. The process happens by itself.”

The BNR is a central feature of the new 8 mgd (design) facility, which went online in September 2012. The 18-member staff made a smooth transition from an antiquated plant to the new facility’s modern technology. Among various honors, the plant earned the 2013 Governor’s Environmental Excellence Award.

Out with the old

The City of Clinton (population 27,000) built the new facility in response to a consent decree imposed in 2009 by the state attorney general’s office. The old treatment plant was built in 1963 and upgraded in several stages to an activated sludge process in the 1970s.

In the mid-1990s, the aeration tanks were retrofitted with fine-bubble ceramic disc diffusers, and capacity was expanded with addition of a clarifier and a digester. Projects in the next decade included replacement of a failed digester cover, replacement of influent pumps and addition of influent screening. “Starting in the late 1990s, there were some compliance issues,” says Riney, water quality superintendent since 1985. “TSS and ammonia were the two big hitters.”

Then there was the matter of overflows. “We have a combined sewer system, and flows would shoot up to nearly 26 mgd during major rain events,” Riney says. “The consent decree mandated a new treatment plant and a long-term control plan to eliminate combined sewer overflow [CSO] discharges.

“The treatment plant project has cost us $70 million. Our estimate for the 25 years we’ve been given to do collection system work is in the neighborhood of $120 million. It involves separation of the sewers and replacement of at least four major pump stations that are more than 40 years old.” The aim is to reduce CSOs to four to six per year.

At present, says Milroy, “There are spots along the river that overflow when the collection system gets overwhelmed. One lift station alone averages 25 to 30 CSOs per year.”

Working together

Because the old facility was landlocked, a rehabilitation and expansion project was not an option. “Building a new plant on virgin ground — that was a given,” Riney says. “With that empty palette in front of us, we talked about how big to build it to allow for economic development.”

During those discussions, the cities of Camanche (population 6,000) and Low Moor (500), facing major upgrades to their treatment systems, approached Clinton about taking their wastewater. Meanwhile, the state Department of Natural Resources had assembled a team to develop what is now known as the Iowa Nutrient Reduction Strategy.

In that environment, the firm, HDR, designed the facility and included the BNR process at an incremental cost of “probably less than $1 million,” says Riney. “It seemed like a logical thing to include. It was apparent that if we were to wait and add BNR on later it would cost a lot more,” possibly more than $4 million.

At present, the Clinton permit calls only for monthly monitoring of total nitrogen and total phosphorus. “Our monitoring shows that we are already in compliance with the 10 mg/L nitrogen and 1.0 mg/L phosphorus standards,” Riney says.

The consent decree said the new plant had to be online by the end of 2012 and in compliance by July 1, 2013. “The new plant first received flow on Sept. 21, 2012, and by that point we had actually managed to bring the old plant into compliance — it had been for about 14 months. We transitioned from the old plant to the new plant and never had a violation.”

Major improvement

The old treatment plant process included screening and grit removal, primary settling, activated sludge treatment and final clarification. Thickened biosolids were anaerobically digested. The new process actually starts at the old plant site. Influent arriving there passes through coarse bar screens (Vulcan Industries) and then is forced about 2.5 miles to the new facility (influent pumps from Pentair – Fairbanks Nijhuis).

At the headworks it passes through perforated plate fine screens (Huber Technology) and a PISTA Grit Chamber vortex grit removal system (Smith & Loveless). A splitter box then diverts the flow directly to three racetrack-style oxidation ditches (designed by HDR). There is no primary settling step.

In the BNR process, the wastewater passes through anaerobic, anoxic and aerobic zones. Aeration is provided by three 150 hp HSI turbo blowers (Atlas Copco) and fine-bubble diffusers (Sanitaire – a Xylem Brand). Waste activated sludge is delivered to four aerobic digesters aerated by four 100 hp HSI turbo blowers (Atlas Copco) and coarse-bubble diffusers (Sanitaire).

The aeration process is automated through a feedback loop. A dissolved oxygen probe (Hach Company) in each basin regulates blower activation and speed by way of upper and lower setpoints. The blowers are equipped with variable-frequency drives. The system is set to hold DO in the basins at about 2.0 mg/L.

After aeration, the flow passes to three final clarifiers (Evoqua Water Technologies). Final effluent flows to a pump station (Pentair - Fairbanks Nijhuis) and is sent back to outfall at the former facility. There is no disinfection now, but UV disinfection will be added by 2017 to comply with the consent decree

Results delivered

The biggest improvement so far has been in process stability in the face of wet weather. The new plant can treat a maximum wet-weather flow of 17 mgd. As insurance against such events, the old plant’s coarse bar screen, grit removal system and the three rectangular primary clarifiers have been converted to a wet-weather retention and treatment facility.

An adjustable weir can be set anywhere between 12 and 17 mgd. Any flow above the weir setting is diverted to the CSO facility for preliminary and primary treatment before discharge to the river. “There is essentially no limit on how much the old facility can take,” says Riney. “We have seen more than 27 mgd.”

Milroy recalls, “During rain events at the old facility, we would wash out everything, and we would have to start all over and re-establish our floc and microbial activity. There was absolutely nothing we could do to keep the solids from going over the side and into the river. It was the most helpless feeling I ever had in this business. Now we don’t even have to think about it. We’ve experienced major rain events through this plant, and we don’t even blink an eye.”

Process automation and a well-trained team keep the plant performing consistently. “The BNR process was new to everyone,” says Riney. “The SCADA system was new. I can’t say enough about the staff. They really did rise to the occasion.” Besides Riney and Milroy, both Grade IV (highest) wastewater operators, the team includes:

  • Mike Baker, pretreatment director/FOG enforcement
  • Rita Schaeffer, administrative assistant
  • Jane Teney, laboratory superintendent (winner, 2011 Iowa Water Environment Association Laboratory Analyst Excellence Award) and Tracie
  • Kelly, laboratory technician
  • Plant operators David Burn, Ken Decker, Mark Krauss and Gaylon Pewe
  • Maintenance operators Scott Shirley, Thomas Witt, Conner Galloway and Ken Jackson
  • Collection system maintenance specialists Elijah Ball, Casey Green and Dan Millard

Thoroughly trained

To get the team acclimated, Riney and Milroy, along with the plant equipment vendors and Lyle Johnson, process specialist with HDR, led an extensive program of classroom and hands-on training for operations and maintenance staff that ultimately encompassed more than 400 hours per person.

“The thing you have to realize is that every single part of this plant was a whole new method of doing things than we had ever done before,” Milroy says. “We might have had a basic idea of grit removal, but this was a totally different kind of grit system. Oxidation ditches are similar to activated sludge, but they work a lot differently. All the technology was new to everybody. It was as new to me as it was to them. It was a matter of working through it together.”

The plant was constructed on a 32-month cycle, and the training began about halfway through. Says Riney, “We were still operating the old facility 24/7. So we shuffled guys in and out of the work schedule for training. We also made a point of taking them out every three months or so during construction and having them tour the new place. We wanted them to get a good view of the plant actually coming up out of the ground. I think that helped quite a bit with the buy-in.

“It has been challenging. Let’s face it — nobody likes change. The staff was a little fearful, but some have been at this for quite a while, and the practices and principles weren’t necessarily new. My hat is off to them for the way they embraced the change. I know they take a lot more pride in this facility than in the old one.”

Taking proper care

Operators are now more involved in basic housekeeping and light planned maintenance (like fluid checks and filter changes) than in the past. Major items like pump and motor rebuilds will remain the province of the maintenance staff. A computerized maintenance management system (AllMax Software) automatically churns out work orders.

The team’s biggest challenge was learning the SCADA system (with Wonderware software from Invensys). Automation at the old plant consisted of one programmable logic controller. Now operators can monitor and control the plant from human-machine interfaces in any of five locations, one in each building.

The plant is staffed seven days a week, eight hours a day. In the off hours, an on-call operator can access the SCADA system using a smartphone and in most cases address issues without reporting to the plant. “We went the smartphone route instead of a laptop because the on-call operator might want to go out to dinner with his family, and this way he’s not lugging a laptop around,” Milroy says.

Getting notice

Since startup, the Clinton plant has been earning recognition from multiple directions. Adam Schnieders, lead author of the Iowa DNR’s Nutrient Reduction Strategy, nominated the plant for the Governor’s Award, “because we were the first and I believe we are still the only BNR facility in Iowa,” says Riney, the 2004 winner of the William D. Hatfield Award from the Iowa Water Environment Association.

The plant also has won the 2013 Project of the Year Award in the $25 million to $75 million category from the Iowa Chapter, American Public Works Association. In addition, it received a Grand Conceptor Award from the American Council of Engineering Companies. Clinton, Camanche and Low Moor earned a 2013 All Star Community Award from the Iowa League of Cities for their cooperation in completing the plant project.

An essential lesson from the experience with the plant is that nutrient removal should not be an object of dread, Riney and Milroy agree. “It’s not the biological nightmare that people are afraid of,” says Riney. “A lot of folks are fighting it. There are court actions against it.

“But we’re not in this business to lawyer up when a new standard comes down the pike. We’re in this business to put out clean water. Just go ahead and do it. Don’t be afraid of it. It is part of the obligation we have to the environment.”  

More Information

AllMax Software, Inc. - 800/670-1867 - www.allmaxsoftware.com

Evoqua Water Technologies, LLC - www.evoqua.com

Fournier Industries, Inc. - 418/423-6912 - www.rotary-press.com

Hach Company - 800/227-4224 - www.hach.com

HDR - 800/366-4411 - www.hdrinc.com

HSI Blowers - 800/725-2291 - www.hsiblowers.com

Huber Technology, Inc. - 704/949-1010 - http://huberforum.net

Invensys Operations Management - 949/727-3200 - www.iom.invensys.com

Parkson Corporation - 888/727-5766 - www.parkson.com

Pentair - Fairbanks Nijhuis - 913/371-5000 - www.fairbanksnijhuis.com

Sanitiare - a Xylem Brand - 855/995-4261 - www.sanitaire.com

Smith & Loveless, Inc. - 800/898-9122 - www.smithandloveless.com

Vulcan Industries, Inc. - 712/642-2755 - www.vulcanindustries.com



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