Farm ‘bioreactor’ will filter nitrate from water – Quad City Times

A lawsuit filed two years ago by the Des Moines Water Worksagainst three drainage districts in northwest Iowa drew a lot of attention to agriculture-generated nutrients in Iowa's streams and rivers.

The water works gets its drinking water from the Raccoon River. When nitrate levels reach a certain level, specialized and expensive equipment is required to remove thenitrate and make the water safe for drinking.

The lawsuitclaimed thenutrients were coming from nitrogen fertilizer and, in some cases, animal waste viaunderground drainage tiles used on farms. Although the lawsuit was dismissed in March, the questions it raised remain.

The state of Iowa has adopted avoluntary Nutrient Reduction Strategy, inspiring more strategies for filtering farm water before it reaches streams. One such strategy is the installation of"bioreactors" at the edge of fields.

Here's how it works: A bioreactor is a trench filled with wood chips. When water flows into it, the bacteria in the water "eats" the wood chips, then "breathes" the nitrate, converting it into nitrogen gas. That way, cleaner water is discharged into waterways.

Scott Countyfarmer Robb Ewoldt installed the area's first known bioreactor on land he farms in Muscatine County inApril. He calls it a"denitrification plant."

The process is relatively new and construction is costly, anywhere from$12,000 to $20,000, depending on the size and slope of the land.

Ewoldt's was on the high end, about$20,000. In his case, he was able to obtain "cost-share" payments of about one-third from water-quality initiative funds at theIowa Department of Agriculture and Land Stewardship andabout one-third from theIowa Pork Producers Association. The rest he paid for himself.

Given the cost and the fact there are thousands and thousands of drainage tiles in Iowa, bioreactors are not likely to become widespread any time soon. But they are a start.

There's not much to see

The trench for Ewoldt'sbioreactor is 100 feet long, 25 feet wide, eight feet deep and filled with about 440 cubic yardsof wood chips that were trucked in from Washington, Iowa. The tile that flows into it drains about 50 acres, he said.

Ewoldt applies hog manure to the field in the fall as fertilizer; his manure management plan filed with the Iowa Department of Natural Resources allows him to apply 3,750 gallons of manure per acre per year.

Weekly water samplingby a technician with the Iowa Department of Agriculturewill show what affect the manure and the bioreactor have on nitrate levels. At the time the reactor was installed, levels were at four parts per million, which was well below the 10 parts per million that is acceptable for drinking water, said Jim Gillespie, director of the Agriculture Department's Division of Soil Conservation and Water Quality.

After installation, the percentage has fallen to one part per million.

Because all the action is underground, there's really nothing to seeon the surface, except for two small metal boxes that control the water flow. It is sometimes necessary to slow the water coming into the bioreactor, so the bacteria have time towork and, if the rainfalling on the field is too much for the bioreactor to handle, the water-flow structures allow it to bypass the bioreactor and go directly into the stream.

In Ewoldt's case, water flows into an unnamed tributary of Pine Creek.

Generally speaking, about 45 percent of the total cost of bioreactor installation is for wood chips, 30 percent is for the water-control structures and tile, 23 percent is for the earthwork and 2 percent is for a protective fabric between the wood chips and the soil underneath, according to Sara Klindt, a soil conservation technician withthe Iowa agriculture department office in Muscatine.

Carbon from the wood chips is what the bacteria eat, and it is not yet known exactly how long the wood chips will last before they need to be replaced, Gillespie said. He is hoping for a lifespan of at least 10-15 years.

In Ewoldt's case, the earth work costs went up, because more trenching was required to get the drainage right than originally anticipated.

State, Pork Producers helped

To date, the Soil Conservation and Water Quality Division of the Iowa Department of Agriculture has funded five bioreactors across the state and has 11, including Ewoldt's, in process,Gillespie said.

The state will reimburse up to 50 percent of the cost, but of course, there is only so much money to go around. In fiscal 2016, the division received $9.6 million for all water-quality initiatives statewide and, for 2017, received $10.575 million, Gillespie said.

Ferreting out other avenues of funding, such as Ewoldt did with the Pork Producers, makes bioreactors more affordable, Gillespie said.

The Pork Producers Association has committed to providing up to $25,000 through the year to offset up to half the costs for hog farmers to install bioreactors or another system called saturatedbuffers on their land, said Tyler Bettin, state public policy director for the association.

Farms are selected based on the greatest opportunity for nitrate reduction and will be dispersed throughout the state to aid in education and demonstration opportunities,Bettin said.

"Projects like this offer excellent opportunity to showcase new nutrient-reduction technologies and further advance farmer-led water-quality efforts in Iowa," he wrote in an email.

Iowa'svoluntaryNutrient Reduction Strategywas adopted about 4 years ago. It aims to reduce by 45 percent the amount of nitrogen and phosphorus flowing down the Mississippi River to the Gulf of Mexico.

Critics have argued that the strategy doesn't go far enough, because there are no mandatory requirements and there is no deadline for reaching the reduction goal. They also question why, when 90 percent of the nutrients causing the "dead zone," or low-oxygen areas, can be attributed to agriculture (farm fertilizer and animal operations) and 10 percent to industry or city treatment plants, only the 10 percent is regulated.

The agriculture community opposes mandatory requirements.

Gillespie points out that none of the work or expense of bioreactors does anything toimprove yields or a farmer's profits. In fact, it is an expense. They are installed to "build a legacy," he said. "They're built so you can say, 'I'm cleaning the water.'"

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Farm 'bioreactor' will filter nitrate from water - Quad City Times