KPI #1: Improved understanding of performance of woodchip bioreactors for removal of phosphorous and bacteria. As more livestock are reintegrated into the Iowa landscape, we need to improve understanding of the strategies available to remove multiple contaminants prior to tile drainage discharge to surface waters. Measured by outreach activities described below. Progress evaluation at June 2017.

KPI #2: Data on measured hydraulic retention times in ISA demonstration bioreactors to determine of actual retention times differ from theoretical retention times based on reactor size. Measured by information generated to inform future bioreactor design. Progress evaluation at June 2017.

KPI #3: Proof-of-concept data on electrical augmentation of woodchip bioreactors for improved NO3-N removal. Potential for reduced cost for nitrate removal on a per pound basis. Measured by the next step which is application of the concept at the pilot scale or as an on-farm demonstration. Progress evaluation at March 2017 and August 2017.

The long-term outcome of this study would be to inform design recommendations for wood chip bioreactors for installation when multiple contaminants are of concern (nitrogen, phosphorous, and bacteria). Our hope is that these efforts will lead to fewer impaired waters, healthier animals, protected public health, and more sustainable agricultural systems.

This information will be important for producers who are making management decisions and for state agencies that have responsibility for water quality. Producers will have valuable information to help guide selection, design and implementation of bioreactors to remove contaminants from tile drainage water. Policy makers will have new information on a popular management practice when impaired waters require multiple strategies to improve water quality as part of a watershed management plan.

Update:

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This project assessed the potential of woodchip bioreactors to remove multiple water quality contaminants, including nitrogen, phosphorus and bacteria, which are especially important in agricultural landscapes with integrated livestock and cropping systems. While much emphasis in Iowa has been focused on nitrate removal, it is equally important to consider removal of phosphorous and bacteria to meet the goals of the nutrient reduction strategy and to address impaired waters across the state. We addressed this goal by monitoring several field bioreactors located on private land and also by conducting laboratory experiments. Our field results generally showed reduction of fecal indicator bacteria concentrations, but we found mixed results for phosphorus removal. New studies are suggesting that materials designed to sorb phosphorus such as steel slag need to be added to bioreactors for consistent phosphorus removal to be achieved. Both our field monitoring and laboratory experiments show that woodchip bioreactors have potential to remove bacteria.
The second phase of the project addressed a new method to increase nitrate removal in woodchip bioreactors through electrical stimulation. As this practice has not been previously studied in a woodchip environment, our work was conducted in the laboratory. From our work we have shown that the electrical stimulation does indeed lead to increased nitrate removal and we also identified design parameters under which the electrical stimulation is likely to be most cost effective. The NO3-N removal cost ($4.49/kg-N) using electrically stimulated woodchip bioreactors is still within the range of other BMPs costs ($0.12 to $36.00), and thus we conclude that this treatment is a viable alternative when nutrient removal is of high priority.