[Effects of benzene, toluene on reductive dechlorination of trichloroethylene and its daughter product cis-1,2-dichloroethylene by granular iron].
Mixed plumes contained chlorinated solvents and petroleum hydrocarbons which mainly refers to BTEX (benzene, toluene, ethylbenzene and xylenes) in groundwater can be remediated by sequential units combined an iron permeable reactive barrier (Fe0-PRB) with an anoxic wall. In design of the Fe0-PRB it should be taken into account the necessity of altering the width of the iron cell in the presence of BTEX. Three column experiments were conducted to evaluate the effects of benzene, toluene on the long-term performance of reductive dechlorination of trichloroethylene (TCE) by granular iron. The results showed that the kinetics of TCE (at the initial concentration of 2 mg x L(-1) more or less) reduction was accorded with pseudo first-order even in the presence of benzene or toluene (at about 1-2 mg x L(-1), respectively). The existence of benzene and toluene inhibited the removal of TCE by 15.1% and 18. 5% , respectively; however, the presence of benzene slightly increased cis-1,2-DCE reduction rate by 4.5%, and the presence of toluene increased cis-1,2-DCE reduction rate by 42.8%. The inhibition of benzene and toluene other than mineral precipitates was not one of the decisive factors in the long-term performance of an Feo-PRB; in addition, the kinds of chlorinated daughter products of TCE in the presence/absence of benzene or toluene were identical and cis-1,2-dichloroethylene (cis-1,2-DCE), the major intermediate, firstly broke through from all the 3 columns at concentrations about 2-75 microg x L(-1), indicating that designing the width of an Fe0-PRB should be based on the hydraulic residence time of cis-1,2-DCE. In conclusion, if only considering the TCE remedial goals and disregarding the effects of cis-1,2-DCE on BTEX biodegradation downgradient the Fe0-PRB, the results suggested that it should be not necessary to increase the width of the iron cell for constructing sequential permeable reactive barriers (SPRBs) to rescue TCE- and BTEX-contaminated aquifers.
Liu
Yu-long
YL
Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China. liuyulong98@yahoo.com.cn
Xia
Fan
F
Liu
Fei
F
Chen
Hong-han
HH
D001554:Benzene / Q000737:chemistry / Q000302:isolation & purification*; D004000:Dichloroethylenes / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D010084:Oxidation-Reduction; D014050:Toluene / Q000737:chemistry / Q000302:isolation & purification*; D014241:Trichloroethylene / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
D004000:Dichloroethylenes; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D014050:Toluene; D007501:Iron; D001554:Benzene; C035384:1,2-dichloroethylene