Enhance Of Trichloroethylene Aerobic Biodegradation By Hydrogen Peroxide As The Oxygen Source In The Groundwater

Trichloroethylene (TCE) is a common organic pollutant and is widespread in soil and groundwater, which pollutes the environment seriously. Aerobic biological treatment is an effective method for remediation of TCE. But air needs to be continuously supplied to meet the requirement of aerobic degradation due to the low concentration of dissolved oxygen in the groundwater. In this study, a bacterial community was enriched from TCE-contaminated soil to degrade TCE in the presence of H2O2which served as oxygen-supplier and the optimal growth and degradation pH and inculum for TCE-degrading enrichment were7.0and10%respectively. The enriched cultures were acclimatized to H2O2by gradually increasing the concentrations of H2O2. The enrichment could degrade120mg/L TCE within12d by using8mM H2O2as the sole oxygen source. The bacterial community induced catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) to decompose H2O2and reduce the toxicity.16S rRNA gene cloning and sequencing showed that the dominant species in the enrichment clustered in three phyla: Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Bordetella, Stenotrophomonas, Sinorhizobium, Variovorax and Sphingobium were the dominant species. PCR detection of the genotypes of the key enzyme involved in the bacterial TCE degradation revealed that phenol hydroxylase (Lph) gene participate in the epoxidation of TCE. As for two high efficient TCE-degrading bacteria (Burkholderia cepacia and Pseudomonas putida) which have been already isolated, their degradation rates of TCE were1.201mg/L·day and1.144mg/L·day respectively when used4mM H2O2as the oxygen source. The results are significant for understanding TCE biodegradation in the presence of H2O2via the identity of microbes and it will also contribute to the potential applications of an aerobic process for in situ bioremediation of TCE-contaminated groundwater.