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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #345850
Title: Impact of temperature and hydraulic retention time on pathogen and nutrient removal in woodchip bioreactors

Author
item SOUPIR, MICHELLE - Iowa State University
item HOOVER, NATASHA - Iowa State University
item Moorman, Thomas
item Bearson, Bradley - Brad
item LAW, JI YEOW - Iowa State University

Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2017
Publication Date: 3/1/2018
Citation: Soupir, M.L., Hoover, N.L., Moorman, T.B., Bearson, B.L., Law, J.Y. 2018. Impact of temperature and hydraulic retention time on pathogen and nutrient removal in woodchip bioreactors. Ecological Engineering. 112:153-157. https://doi.org/10.1016/j.ecoleng.2017.12.005.

Interpretive Summary: Woodchip denitrification bioreactors are an important edge-of-field practice for treating agricultural drainage; however, their ability to filter microbial pollutants has only been explored in the context of wastewater treatment. Upflow column reactors were constructed and tested for E. coli, Salmonella, NO3-N, and dissolved reactive phosphorus (DRP) at hydraulic retention times (HRTs) of 12 and 24 h and at controlled temperatures of 10 and 21.5ºC. Influent solution was spiked to 30 mg L-1 NO3-N, 2-8×105 E. coli and Salmonella, and 0.1 mg L-1 DRP. Microbial removal was consistently observed with removal ranging from 75–78% reduction at 10ºC and 90-96% at 21.5ºC. The concentration reduction ranged from 2.75 to 9.03×104 for both organisms. HRT had less impact on microbial removal than temperature and thus further investigation of removal under lower HRTs is warranted. Nitrate concentrations averaged 90% reduction in columns at room temperature 21.5 C and 24 HRT and 29% reduction from columns at 10 C and 12 HRT. DRP removal was likely temporary due to microbial uptake. While potential for removal of E. coli and Salmonella by woodchip bioreactors is demonstrated, system design will need to be considered. High concentrations of these microbial contaminants are likely to occur during peak flows, when bypass flow may be occurring. The results of this study show that woodchip bioreactors operated for nitrate removal have a secondary benefit through the removal of enteric bacteria.

Technical Abstract: Woodchip denitrification bioreactors are an important edge-of-field practice for treating agricultural drainage. However, their ability to filter microbial pollutants has only been explored in the context of wastewater treatment. Upflow column reactors were constructed and tested for the bacteria E. coli and Salmonella, NO3-N, and dissolved reactive phosphorus (DRP) at hydraulic retention times (HRTs) of 12 and 24 h and at controlled temperatures of 10 and 21.5ºC. Removal of was consistently observed with removal ranging from 75–78% reduction at 10ºC and 90-96% at 21.5ºC. Retention time in the reactors had less impact on microbial removal than temperature. Nitrate concentrations averaged 90% reduction in columns at room 21.5 C and 24 HRT and 29% reduction from columns at 10 C and 12 HRT. DRP removal was likely temporary due to microbial uptake. While potential for removal of E. coli and Salmonella by woodchip bioreactors is demonstrated, system design will need to be considered. High concentrations of these microbial contaminants are likely to occur during peak flows, when bypass flow may be occurring. The results of this study show that woodchip bioreactors operated for nitrate removal have a secondary benefit through the removal of enteric bacteria. The results of this research inform scientists and engineers, and water quality specialists about this additional benefit of this technology.