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Reclaiming Water

Nothing can be sustained without water, including industry. Once considered a free and unlimited resource, water is now a limited resource in many parts of the United States, forcing communities and industries to conserve and recycle water.

Minnesota, fortunately, has not faced water shortages like California and Florida. But some Minnesota regions do have limited groundwater supplies that could hamper construction of new ag-processing plants there, says Jen Wagner-Lahr, AURI project director.

AURI and Metropolitan Council Environmental Services are collaborating on a study to look at using “reclaimed water” from municipal wastewater treatment plants for nonpotable ag-processing uses.

In Minnesota, agriculture uses about 40 percent of groundwater supplies. While only one percent of that is for biofuels production, ethanol critics frequently point to the fuel’s water use.

“Ethanol has come under fire — water use is a big thing that critics use against the renewable fuel,” Wagner-Lahr says. It’s arguable that petroleum production requires more water than ethanol, but a more palatable solution is to recycle water rather than pull fresh supplies from the ground.

MCES’ portion of the study, conducted by Craddock Consulting Engineers of St. Paul, found that using reclaimed water is most economical for ethanol plants close to a wastewater treatment facility with high-quality effluent. “Getting reclaimed water to the ethanol plant is a huge part of the cost,” says Deborah Manning, MCES principal engineer.

Ethanol plants are most likely to use reclaimed water for cooling, which requires more treatment before the ethanol plant can use it, Manning says. Further treating the effluent, which may include chemical additions, filtration and enhanced disinfection, also increases cost.

Regulating water

Changing regulations could impact the economics of using recycled versus fresh water.

The Minnesota Pollution Control Agency is developing a “Total Maximum Daily Load” program that will affect surface water discharges for most communities. For example, the Lake Pepin Watershed’s TMDL will affect nearly two-thirds of the state — including the Mississippi, Minnesota and St. Croix Rivers and all waters that feed into those systems.

“As wastewater treatment plants upgrade to meet TMDLs, their discharge may become closer to what an ethanol plant needs for uses such as cooling water,” Manning says.

Another factor making reclaimed water desirable is groundwater-permitting requirements by the Department of Natural Resources. “As water becomes more scarce, those permits are harder to get — an impetus for people to look at other nonpotable water-supply sources,” Manning says.

Southwest and southeast Minnesota have groundwater limitations, according to the DNR. “Ethanol plants are located in these areas because of proximity to corn. That’s good … but the water supply issue can be a challenge. I would expect people would want to start looking at alternative water supplies,” Manning says.

Recyling now

Some Minnesota communities and ethanol plants are being proactive. The City of Winnebego, for example, discharges about 350,000 gallons of treated wastewater into the Blue Earth River daily. That’s about the same amount of water used daily by the Corn Plus ethanol plant, located just east of Winnebego, which is considering using the treated water in its plant. It would be the state’s first ethanol plant to use recycled water, although a natural-gas powered electrical plant in Mankato is using reclaimed water for cooling.

Wagner-Lahr says there are also ethanol plants in North Dakota and Kansas using reclaimed water. “At the Casselton (N.D.) plant, they are piping water over 25 miles from Fargo; that’s expensive.” The reclaimed water is “not necessarily for their process water but certainly for cooling, nonpotable water,” Wagner-Lahr says.

Statewide, approximately 600 municipal plants yield about 425 million gallons of treated wastewater daily — nearly matching the daily water use of Minnesota industries. In the Twin Cities 7-county metro area, MCES collects and treats about 255 million gallons of wastewater a day at seven facilities.

“There is a question about why MCES is interested in an issue that is more of a Greater Minnesota issue in terms of where ethanol plants are and water supply concerns. However, the Twin Cities metro area has had an ethanol plant and there have been plans for others,” Manning says. “We are interested in reclaimed water; anything we learn can be applied to other sectors.”

Next Step

This summer, MCES completed its portion of the reclaimed water feasibility study. “What we’re looking forward to is … the implementation,” which will include industry forums on the topic led by AURI, says Wagner-Lahr.

“Ideally, we’d like to convene groups of people in a couple of venues,” such as the Corn Growers Association state convention in January, “and ask them, given this information, is this something you would considered implementing? What is it going to take for industry to grab hold of it?”

So far, the reclaimed water-use study shows that “it’s feasible given the right set of conditions,” Wagner-Lahr says.

“Right now a lot of things have to line up for it to be financially viable,” Manning says. “But I do think there are shifts such as TMDL standards that will cause people to look more closely at reclaimed water … it can become a stronger option.

“I would say that if an ethanol facility hasn’t had a conversation with their local wastewater plant, they really should.”