With new discharge system, Bushmills Ethanol expects to shrink its water usage
ATWATER — Bushmills Ethanol is helping lower the bar, and in this case that’s a very good thing.
Bushmills Ethanol on Feb. 28 began operating a newly installed zero liquid discharge system built by U.S. Waters Services of St. Michael, Minn.
It’s the fifth such system the company has installed at ethanol plants in Minnesota, according to Christian Hess, area manager with the water services company.
The $3.8 million inves.tment is expected to reduce the Bushmills Ethanol plant’s overall use of water by one-third.
It works like this: Water that was previously discharged into Judicial Ditch 17, part of the Middle Fork of the Crow River watershed, is now returned and re-conditioned. That in turn reduces the amount of water the plant must draw from its wells, and ends the plant’s liquid discharges entirely.
Bushmills Ethanol General Manager Erik Osmon cautions that it’s too early to know for certain, but he said the new system should reduce the amount of water used per gallon of ethanol produced from about 2.9 gallons to 2 gallons.
Hess noted that when the industry was first launched, the ratio of water to ethanol produced was as much as 11 gallons to 1. The industry has steadily made gains in efficiency: The standard today is believed to be somewhere between 3 to 4 gallons of water per gallon of ethanol produced.
Osmon said it is part of a good neighbor approach by the farmer cooperative.
“We are in Minnesota,’’ said Osmon. “The Pollution Control Agency has made water very much a priority both in quality and the amount used, and we’ve reacted accordingly. They didn’t tell us to do this.’’
Bushmills is in compliance with its discharge permit, but in 2012 it paid civil penalties for previous violations.
The new system allows the plant to recycle the water coming mainly from the cooling system.
The U.S. Water Services system uses a cold lime treatment and softening process, not unlike that used by some municipalities to supply drinking water. At Bushmills, the water drawn from the aquifer and the recycled water are mixed and treated in a multi-step process. All of the elements that are naturally found in the local groundwater — magnesium, iron, strontium, and ferrium among them — are greatly reduced in the softening process.
Their removal benefits operations at the plant, as these minerals otherwise concentrate and adversely affect the plant’s boiler and water cooling systems. The new, largely gravity-fed treatment system also reduces overall energy usage.
An important part of the treatment process involves adjusting the pH of the water with the use of carbon dioxide. Bushmills will be using the carbon dioxide that results from its ethanol production in the water treatment system, furthering reducing its carbon footprint, noted Hess.
The lime used in the treatment process is captured at the end of the cycle, pressed dry and formed into cakes for easy transport. At this point the lime will be placed in an approved landfill. The company is working out an arrangement so that in the future the lime can be spread on farm fields to the east, where it will help reduce soil acidity.
Work on the project began last November, and this winter’s severity made it a challenge for the construction workers, said Hess. Osmon said the project was completed right on schedule and the start-up went very well.
U.S. Water Services has installed similar zero liquid discharge in Minnesota ethanol plants including: Highwater Ethanol, Lamberton; Granite Falls Energy, Granite Falls; Biofuel Energy, Fairmont; and Guardian Energy, Janesville.