Management of phytosanitary effluent: Rinsing and decontamination of empty pesticide containers by bio-detergent

The biotic degradation of organophosphorus (OP) insecticides, especially chlorpyrifos (CP) and dimethoate (DIM), has led to significant interest in their use for decontamination. The aim of this investigation was to use the degrading potential of two bacterial strains to clean up empty pesticide containers. These strains were previously isolated from a Tunisian soil that had received regular treatments with OP insecticides (CP and DIM) for more than five years. Kinetic hydrolysis of CP and DIM in the absence or in the presence of two isolated bacteria Enterobacter cloacae and Serratia rubidaea demonstrated the biodegrading potential of both microorganisms. A rate of chlorpyrifos degradation of 13% was obtained in aqueous medium without bacteria after 2 h whereas the rates were about 36% and 46.7% in aqueous medium with Enterobacter cloacae and Serratia rubidaea, respectively. Dimethoate was also effectively degraded with rates of about 74.7% and 77.3% within 2 h with Serratia rubidaea and Enterobacter cloacae, respectively, compared with 68.6% in the aqueous control solution. Rinsing empty containers once with a bio-detergent based on isolated bacteria, and including an appropriate adjuvant like DMSO (dimethylsulfoxide), resulted in residue levels in the rinsing effluent that were lower than with the triple rinsing recommended by the FAO.