Full-Scale Development and Testing of a System to Manage Pesticide-Contaminated Wastewater

A previous report (Corwin, 1996; Yoder et al., 2001) described a literature and laboratory study examining options for disposing of wastewater contaminated with low concentrations of common pesticides. That report focused on the Soil-Based BioReactor (SBBR) as the best candidate for providing a highly effective means for wastewater disposal at low cost and with low management requirements. Much work had been done on such systems since the 1970s, but little had been done to optimize system management. That report then documented a soil column laboratory study, which indicated very good evaporation and pesticide dissipation results with a specific combination of soil, environmental conditions, and water application method. This study follows up on that report and is meant to address two questions: I) Can the water evaporation and pesticide dissipation results of the first study be duplicated by a full-scale version?; and 2) Is there a reliable and inexpensive way of building such a full-scale soil bed and providing the controls for water application? The study yielded positive answers to both questions. The full-scale soil bed provided evaporation per unit area similar to that in the laboratory soil columns, and slightly more pesticide dissipation. A safe and reliable soil bed was built out of a readily-available high-density polyethylene feed trough supported by a welded channel-iron frame with large casters. The system used to control the water application was driven by gravity and used three float switches, two latching solenoid valves driven by latching relays, and two mechanical float valves. The entire system performed flawlessly during the 60-day trial. These results are then examined for their impact on others attempting to duplicate this scale-up in their specific situation. All indications are that this system could easily be used in a full-scale facility to provide safe and efficient handling of pesticide-contaminated wastewater.