Biodegradation of Tetrachloroethene in Batch Experiment and PHREEQC Model; Kinetic Study

Introduction: Bioremediation and biodegradation are considered as environmental friendly techniques for contaminants’ removal in polluted environment. In this study, the removal and kinetics of Tetrachloroethene (PCE) and Trichloroethene (TCE) microbial degradation, their inhibitory effects and the rate of dehalogenation capacity at high concentration of PCE were investigated.Materials and Methods: Dechlorinating culture was provided by Bioclear B.V. from a PCE-contaminated site (Evenblij in Hoogeveen -The Netherlands). The batch apparatuses were placed in an orbital shaker at 150 rpm at room temperature. In all the 18 batches, 6 different concentrations of PCE were measured from 0.1 mM to 0.6 mM. The degradation rate of PCE, Trichloroethene (TCE), and cis-1,2-dichloroethene (cDCE) were determined by the PHREEQC model.Results: The results revealed that the final product was ethene and the rate of dechlorinating of PCE increased gradually. The degradation process started after 3 days in batch modes (0.1 mM). After 10 days, the dechlorination of PCE to TCE was obtained in a low concentration of PCE (0.1 mM). Also, the TCE concentration became close to zero after 10 days. However, the start point was longer than PCE and the rate of biodegradation of TCE was faster than PCE. PCE did not show any progress in the dechlorinating procedure at 13th and 14th batch series and none of the daughter products were observed.Conclusions: It should be concluded that there was no single organism that could dechlorinate PCE to ethene, directly. Therefore, the best consortium of microorganisms to dechlorinate PCE to ethene faster, with less production of VC as the most hazardous compound, should be studied.