Anoxic/Anaerobic Biodegradation Of Benzene And Toluene Downgradient Of The Fe~0 Permeable Reactive Barriers

The removal of the plumes formed by petroleum hydrocarbon and chlorinated hydrocarbon which commonly exist in groundwater prefers to focus on the utilization of the combined permeable reactive barriers (PRBs) which reduce chlorinated hydrocarbons by Fe and remove BTEX by biodegradation. However, during the run of Fe0-PRB:â… . pH raise;â…¡. Chlorinated hydrocarbon penetrate through the PRB;â…¢. Some byproducts with less chlorine are often produced and penetrate through the Fe0-PRB and enter into the Bio-PRB. It may influence the biodegradation of BTEX. This study concentrates on the research of pH, TCE and cis-1,2-DCE how to affect the biodegradation of benzene and toluene under the anoxic/anaerobic environment. The following conclusions could be found through this experiment:â… . Proper high pH (9.6) could accelerate the biodegradation of benzene, but may be restrain the biodegradation of toluene and the mixture of benzene and toluene. However, the same law exists when pH 10.5.â…¡. During the biodegradation of benzene and toluene with different pH, the existence of TCE may be restrain the biodegradation of benzene or toluene or the mixture of benzene and toluene and this effect will enhanced when the concentration of TCE increased.â…¢. Under the different pH environment, cis-1,2-DCE will restrain the biodegradation of benzene; cis-1,2-DCE may be accelerate the toluene biodegradation when pH (8.0-8.7) is unchanged, but this accelerate effect will change into restrain effect when pH 10.5; however, when benzene and toluene co-exist, cis-1,2-DCE could accelerate the biodegradation of benzene and toluene; this promotion of cis-1,2-DCE may be due to the co-metabolism of cis-1,2-DCE between toluene or the mixture of benzene and toluene.â…£. Which influence so ever the pH, TCE and cis-1,2-DCE make on the biodegradation of benzene and toluene, it does not make effect on the function of enzyme that must be needed in the biodegradation of benzene and toluene and only reduce the species and amount of microbes which could degrade benzene and toluene.â…¤. Microbes will degrade toluene first when benzene and toluene co-exist, the biodegradation rate of toluene is faster than benzene when they co-exist.â…¥. Through the microbe culture and domestication, the microbe species which could degrade benzene and toluene is: Xanthobacter autotrophicus sp.; Bacillus sp.; Sphingomonas sp.; Xanthobacter sp.â…¦. In the Fe0-PRB and BTEX bio-PRB, the pH raise, TCE and cis-1,2-DCE penetrate in Fe0-PRB does not make obvious effect on the bio-PRB, benzene and toluene also could be biodegradation under anoxic/anaerobic environment. The bio-PRB thickness could be properly extended to prolong the water resort time of benzene and toluene in order to remove the benzene and toluene totally.