DEVELOPMENT OF A SYSTEM TO MANAGE PESTICIDE?CONTAMINATED WASTEWATER

Abstract

One of the primary problems related to pesticide use is disposal of the lowconcentration pesticidecontaminatedwastewater resulting from leftover mixes, equipment rinsing, and general cleanup. The costs, safety issues, and potentialenvironmental impacts associated with this pesticidecontaminated waste are major concerns for most applicators. As partof a broad effort by the University of Tennessee Agricultural Experiment Station and the Tennessee Agricultural ExtensionService, researchers have been carrying out a series of projects that will result in construction of fullscale wastewaterhandling facilities on branch research stations. This study reports on the first project phase, whose objectives were: to choosea wastewater disposal technique from alternatives presented in the scientific literature, and to propose an optimal set ofoperating conditions that could reasonably be followed by typical pesticide applicators.The wastewater disposal technique selected by the study was designated the SoilBased BioReactor, or SBBR. This method,which has been in use for quite some time, involves application of pesticidecontaminated wastewater to soil beds. The waterevaporates from the moist soil surface, and the pesticide is adsorbed to the soil and then broken down by chemical andbiological activity. Earlier studies found this to be an effective technique with no longterm accumulation of pesticide, nomeasurable volatilization of pesticide, and low management requirements. These earlier studies, however, made no attemptto optimize the system, so that became the second study objective.The optimum system resulting from this study used a mediumfine textured soil (a silt loam), operated at a temperatureelevated above the ambient much as would be the case in a greenhouse, and used an application method providing five daysof nearsaturation followed by five days of drying. Under these conditions, and assuming 180 days of wastewater applicationfollowed by 120 days of clean water application, over 98% of atrazine and over 90% of fluometuron active ingredients appliedwith the wastewater had dissipated. The study results indicate that an SBBR system using simple construction andmanagement techniques can effectively dispose of pesticidecontaminated wastewater on a research farm or for a typicalsmall to mediumsize applicator.