Study On Remove Of MTBE From Contaminated Groundwater By Two-layer Permeable Reactive Biobarrier

Permeable reactive barrier(PRB) is an approach developed recently to in situ remediation of the contaminated groundwater. Comparing with pump-and-treat system,the permeable reactive barrier is cheap, durable and have a high efficiency in treatment of contaminated groundwater. As a substituting technology for pump-and-treat method, permeable reactive barriers can effectively remove heavy metals, inorganic anions and organic compounds.So,it will has a good bright prospect future in the remediation of contaminated groundwater.It has been widely used in parctical projects in America and Europe. In this paper we designed a two-layer permeable reactive biobarrier and used dilatant perlite as the adsorption carrier of microbe to focuse on the removal of MTBE in groundwater.The conditions for aerobic biodegradation of MTBE were determined by batch experiments. During biodegradation experiments, TBA was detected and CO₂ was not detectd. Monod model parameters which include the maximum specific substrate utilization rate, half-saturation coefficient and the yield coefficient were measured from batch experiments and fitted by least-square method.The reaction that dilatant perlite adsorb MTBE is a endothermal process. So high temperature is help for adsorption.Adsorption isotherm of MTBE by dilatant perlite was determined to follow Freundlich adsorption by experiments.Vertical hydraulic conductivity of dilatant perlite was measured by penetrate apparatus.Two-layer permeable reactive biobarrier consisted of oxygen-releasing layer and biodegradation layer. The oxygen-releasing layer loaded the mixture of CaO₂, (NH₄)₂SO₄, KH₂PO₄ , inorganic salt and sand. CaO₂ is able to release oxygen upon contact with water. (NH₄)₂SO₄ and KH₂PO₄ were used to supply nutrition for animalcule and drop the pH of the solution. The biodegradation layer loaded dilatant perlite which adsorbed animalcule domesticated by MTBE in their surface. MTBE in polluted water was the only carton source for biodegradation. Concentration of MTBE droped with 45.71% after polluted water thrilled through permeable reactive biobarrier. TBA is byproduct during biodegradation which was detected in barrier experiment.