2018 ASHS Annual Conference

Pesticides subject to runoff from agricultural production contribute to non-point source pollution, where the effects on human and ecosystem health are of concern. Treating agricultural effluent prior to off-site discharge, or for recycling as irrigation, stands to benefit the environment and increase the sustainability of plant production. Agrichemicals can be remediated from water through microbially-mediated breakdown, as well as through sorption. In this study, a two-stage treatment system was constructed combining both processes, with water being provided at a consistent flow-through rate of 1.3 Liters per minute for a total of 625 Liters per day. Woodchips served as a carbon substrate in the first stage to allow the proliferation of denitrifying and pesticide degrading microbial communities, while a calcined shale product was used in the second stage as the sorptive medium. Simulated runoff containing representative amounts of fertilizer and pesticides were supplied to the treatment systems, with influent and effluent concentrations measured at each stage. Initially an incubation period with influent containing only nutrients (20 ppm nitrate, 3 ppm phosphate) was provided to allow development of microbial populations prior to incorporation of three pesticides, oxyfluorfen, chlorpyrifos, and bifenthrin at rates between 1 and 2 ppb. At critical stages throughout the study, the microbial communities in the treatment systems were isolated and comparisons were made between the consortiums found in the nutrient only and the nutrient and pesticide treatments. Throughout the course of the study, effluent contents were monitored to determine the effects on the microbial communities and the saturation point of the sorptive materials. The remediation potential of nutrients and pesticides by these treatments will be presented, as well as population shifts in microbial communities throughout the study.