Sulfadimethoxine is a widely used sulfonamide veterinary antibiotic and could be a source of agricultural contamination. Therefore, information is needed about its degradation kinetics in manure under aerobic conditions. Based on the analysis of first-order kinetics and the assumption that sulfadimethoxine availability for degradation in manure could be limiting, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterile manure was found to be much lower than in nonsterile manure, indicating that biodegradation was significant. In biologically active manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the activity of the degrading microorganisms was inhibited. Increasing moisture or temperature was found to increase sulfadimethoxine degradation in manure. Mixing manure containing high levels of sulfadimethoxine with manure containing lower levels may result in more rapid degradation, thus greatly diminishing sulfadimethoxine contamination in manure and significantly reducing sulfadimethoxine inputs into the environment. During treatment, keeping the manure moist and storing in a moderately warm place under aerobic conditions may also help to diminish sulfadimethoxine contamination.

An advanced oxidation process, anodic Fenton treatment (AFT), and a mixed microbial culture were used to degrade metribuzin [4-amino-6-tert-butyl-3-methylthio-1,2,4- triazin-5(4H)-one], a broad-use triazinone herbicide. Complete and rapid removal of metribuzin was demonstrated. The appearance and subsequent degradation of metribuzin oxidation products--deaminated metribuzin (DA), diketo metribuzin (DK), as well as the production of deaminated diketo metribuzin (DADK)--were observed. To support the use of AFT as a chemical pretreatment, the ratio of 5-day biochemical oxygen demand (BOD5) as measured in the standard test to chemical oxygen demand (COD) was investigated, and an increase from 0.03, a nonbiodegradable solution, to 0.35, a biodegradable solution, was observed. This increase in biodegradability was associated with decreased metribuzin, DA, and DK concentrations and increased DADK concentration. AFT effluent was inoculated with either an enriched microbial culture or Polyseed, a commercially available inoculum. Although there was minimal biodegradation of the remaining metribuzin, there was a significant decrease in DA concentration in inoculated incubations compared with sterile controls after 5- and 10-minute AFT treatment. The enrichment inoculate appeared more adapted toward the less-oxidized, 5-minute-treated effluent, whereas the Polyseed culture, developed to degrade complex waste solutions, appeared to be more effective in a moreoxidized, 10-minute-treated, and potentially more complex effluent. This research supports the continued investigation of AFT and biodegradation as a binary treatment of aqueous pesticide wastes.