Study On Evaluating A Multi-media Permeable Reactive Barrier To Remove Chlorohydrocarbon And BTEX From Groundwater

Because of the increasing organic contaminates and more complicated pollutedsituation, develop a single technology that can easily remove these contaminates isextremely urgent. According to this we carry out a new multi-medium permeablereactive barrier (PRB) which is based on the widely applied technology ingroundwater contaminates remediumtion by combining zero-valent iron barrier withbioremediation barrier in one PRB engineering to remove chlorohydrocarbon andBTEX mixed pollution from groundwater.The research make a thorough inquiry on the pollution removal capabilities andlong-term performance of the multi-medium PRB by column and field experiments.In the column experiment, we set up two columns one is normal column the other isbiological sterilized column to be the comparative experiment. We taketrichloroethylene as the representative of the chlorohydrocarbon pollution，benzeneand toluene as the representative of the BTEX pollution. According to the result wecome up with the following conclusions:(1) Two columns can completely remove thechlorohydrocarbon from groundwater at the beginning of the experiment in theZVI-PRB. Normal column can remove benzene and toluene in the Bio-PRB becauseof the microorganism we put in it;(2) The ZVI-PRB in normal column can notremove all TCE until the70th pv TCE go through the30cm long ZVI-PRB.Bio-control column lost the capabilities of removing TCE as we add a large amount ofnitrate ion.(3) Microorganism can easily survive and grow in the high pH valuesurroundings down gradient of the ZVI-PRB, and bring it down to a suitable value formicro-biological degradation of benzene and toluene when the groundwater flows intoBio-PRB. Also the Bio-PRB keeps a high removal rate of benzene and toluene.(4) Inour study we get a conclusion that Fe（Ⅲ） is the electron acceptor in the microbialdegradation of benzene and toluene downstream though Fe（Ⅲ） and SO42-both canbe the acceptor.In the field experiment the following conclusions were obtained:(1) The plumeappears when TCE get into groundwater. TCE lags behind the groundwater in the soil.(2) ZVI-PRB has a remarkable capability on the removal of high concentration TCE.But it lose this capability in about60days in this experiment because of the highconcentration NO3-. So we put forward that passivation caused by NO3-can result in substantially decreased rates of chlorinated solvent removal.(3) As the fieldexperiment has a shallow groundwater level and there is lots of O2,Fe（Ⅲ）,NO3-andmany other electron acceptors in the water, toluene was removed quickly and keeps ahigh removal rate when it gets into the experiment equipment.In conclusion the new multi-medium PRB is apparent useful in removing TCE,benzene and toluene in the groundwater. But NO3-has a strong influence on theserves life of the ZVI-PRB. We can combine multi-medium PRB with NO3-restoringmethod together to solve this problem.