Treatment of agricultural tile drain water through current designs of bioreactors is mainly through horizontal flow through the bioreactor media. A typical horizontal bioreactor consists of a narrow (<1 m wide) trench, 1 to 1.5 m deep and 10’s of meters long filled with sources of carbon which may include saw dust, wood chips or corn cobs. It is difficult to know how much of the reactive area of the bioreactor is involved when water flows horizontally as preferential flow patterns may bypass zones within the bioreactor. The longevity and maintenance of bioreactors is not fully known because there are very few long-term bioreactors sites in existence.
We designed a novel modular bioreactor for nitrate removal from agricultural drainage water that would have a short hydraulic residence time (HRT) and would be easy to maintenance. The prototype design consists of the elements shown in the figure below. The system is designed for installation adjacent to individual tile outlets along a drainage ditch in order to remediate nitrate. The number of modules installed at a particular location would be in part determined by the size of the outlet pipe and the desired treatment efficiency (hydraulic residence time and/or nutrient reduction).
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