News Feature | August 7, 2017

Woodchip Bioreactors May Help Farmers With Nutrient Removal

Sara Jerome

By Sara Jerome

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Water utilities and farmers are at odds over who should shoulder the burden of cleaning nitrates and phosphorus out of water. Now, a new system called the woodchip bioreactor may make it easier for farmers to clean up pollutants on farms before they diminish water quality.

Laura Christianson, a researcher who works on water quality issues at the University of Illinois, is an expert in woodchip bioreactors. Her work has demonstrated the potential for woodchip-filled trenches to remove pollutants from water on farms.

In a new journal article published in Water Research, Christianson and her team put the denitrifying woodchip bioreactor to the test. They also used filters as part of the experiment.

"The woodchips and the nitrate are necessary for the bacteria to complete their life cycles. As they consume the nitrate, it is removed from the water. It's a biological process," Christianson said in a statement from the university.

The findings, per the journal article, which refers to phosphorus as “P” and nitrogen as “N”:

  • Pairing woodchip bioreactors and P-filters provides unique dual nutrient removal.
  • Woodchip bioreactors upstream of the P-filters optimized dissolved P removal.
  • There were no significant differences in N removal between treatments.
  • Undesirable pollution swapping by-products varied based on flow conditions.
  • The mine drainage residual P-filters were generally better than the steel slag.

Farm runoff poses a major water pollution problem, and many water utilities say farmers should do more to foot the bill to remove them. One Iowa water utility tried to take farming interest to court to pay for the problem, but was not successful, according to The Des Moines Register.

One consequence of nutrients in water is toxic algae. Cyanotoxins, produced by algae, are a nagging problem for the water industry.

Former American Water Works Association (AWWA) President John Donahue described the issue as follows in testimony to Congress:

“There is no uncertainty about one critical aspect of the problem: It is always associated with amounts of nitrogen and phosphorus in the water,” Donahue said, per Roll Call. “Although each watershed is unique and has its own mix of nutrient sources, across the nation the most prominent uncontrolled sources of nitrogen and phosphorus are non-point sources — that is, runoff. These sources are at the same time both the hardest to manage and the furthest from being subject to meaningful federal regulatory authority.”

For similar stories visit Water Online’s Nutrient Removal Solutions Center.

Image credit: "Agricultural runoff," eutrophication&hypoxia © 1999, used under an Attribution 2.0 Generic license: