Amending woodchip bioreactors with water treatment plant residuals to treat nitrogen, phosphorus, and veterinary antibiotic compounds in tile drainage

Treatment of drainage from agricultural production systems is one means to help improve water quality. Treatment of multiple pollutants, such as nitrogen and phosphorus together is a desirable attribute of systems that treat drainage and runoff from agricultural fields. In this study, the performance of inline woodchip (WC) only and woodchip bioreactors amended with 10% and 20% (vol) alum-based drinking water treatment plant residuals (WTR), were evaluated for treatment of N, P, and veterinary antibiotic compounds in tile drainage from field plots during, primarily, the <5 oC non-growing season (fall 2013 to spring 2014) following land application of liquid swine manure (LSM) in fall. Removal efficiencies for both WC + 10% WTR and WC + 20% WTR amended bioreactors were significantly greater than woodchip only bioreactors for nitrate (NO3-N), total phosphorus (TP), and dissolved reactive P (DRP) (p < 0.05). Median removal efficiencies for NO3-N ranged from 33% (WC) to 74% (WC + 20% WTR). For total P, median removal efficiencies ranged between 28% (WC) to 64% (WC + 10% WTR), and for DRP they ranged between 35% (WC) to 89% (WC + 10% WTR). Removal efficiencies for NH4-N were not significantly different between WTR-amended and woodchip bioreactors. Removal efficiencies for a suite of veterinary antibiotic parent and transformation products, such as tylosin, chlortetracycline, and isochlortetracycline, were very high for all treatment systems (>80%); albeit often input concentrations were in the lower ng L−1 range. This study demonstrated the utility of reusing industrial waste products in bioreactors designed to treat tile drainage effluent from agricultural field plots over a Canadian winter period following the land application of liquid swine manure.