The degradation of DEP contaminated soil was studied in the soil slurry phase sequencing batch reactor (SS-SBR). Experiments were conducted for studying the degradation of DEP using four different reactors. Effect of bioaugmentation using ETP microllora on the degradation of DEP was also investigated and found an enhanced degradation. The reactors were operated with a total cycle period of 48 h, comprising one and half hours of fill 45 h of react and one and half hours of decant phases. The metabolites for the DEP degradation in slurry phase have been identified. During the operation of bioaugmented reactor, the substrate partition data showed higher desorption of DEP from soil phase to aqueous phase compared to other reactors studied. The degradation of DEP in the slurry phase confirmed to zero order kinetic equation in bioaugmented reactor. The half life period of DEP degradation in the soil phase of bioaugmented reactor was 19 days. Process performance during the investigation was monitored by determining dissolved oxygen (DO), pH, oxygen consumption rate (OCR) and substrate concentration by high performance liquid chromatography (HPLC). (c) 2005 Elsevier Ltd. All rights reserved.