Degradation Of Tetrachloroethene By Several Co-metabolism Substrates In Groundwater

The contamination of tetrachloroethene, i.e. PCE, in groundwater arouses seriousconcern and how to remove it is payed much attention. Biodegradation throughco-metabolism of microbes is one of efficient ways. Under anaerobic conditions, PCE isbiodegraded through reductive dechlorination and the removal rate is faster with theco-metabolic substrate than without that. Aim to study the degradation of PCE with differentsubstrates, methanol, ethanol, formate, acetate, lactate, glucose and yeast extract included,the anaerobic microbes are cultivated and domesticated to degrade the PCE. The reactionkinetics, influent factors and mechanism are also studied.(1)Batch experiments are performed to cultivate and domesticate microbes. The resultsshow that anaerobic microbes are mature after 11-day cultivation in the surroundings of soiland anaerobic sewage or sludge with the index of COD removal rate. During thedomestication of anaerobic microbes under the mentioned seven substrates and PCE withdifferent concentrations, PCE is transformed into TCE and DCEs through reductivedichlorination. At the 8th domestication, that the removal rates of PCE in several substratesexceed 90% shows the anaerobic microbes are suit to degrade PCE at this time.(2)The batch experiments of degradation of PCE are performed at two conditions ofyeast extract appended and not, respectively. The results show that PCE can be reductivedechlorinated under the mentioned seven substrates and the reactions are coincident with thefirst order kinetics with the regression coefficients exceeded 0.86. PCE is degraded intoTCE and DCEs when yeast extract is appended and the sequence of reaction rate constant ofsix substrates is k_acetate≈k_glucose>k_lactate≈k_ethanol>k_formate>k_methanol>k_yeast, which showsacetate and glucose are the most efficient co-metabolic substrate. By contrast, DCEs are nodetected without yeast extract appended, and the sequence of reaction rate constant of sixsubstrates is k_ethanol≈k_glucose>k_methanol>k_lactate>k_acetate>k_formate>k_compare, which showsethanol and glucose are the most efficient co-metabolic substrate.(3)Yeast extract is not only to be required as a micronutrient for some PCE-degradingsystems, but also can serve as an electron donor for PCE degradation. When it works withother co-metabolic substrates, the mix substrate makes PCE reductive dechlorination betterand accelerates PCE degradation...