The Study On The Petroleum Hydrocarbon Contaminates The Groundwater Renovation By The Permeable Reactive Barrier Of Microorganisms

This thesis carried out an experimental research on the remediation conditions and effects of microorganism permeable reactive barriers(PRB) to the groundwater contaminated by petroleum hydrocarbon. First of all,cold acclimation method was used for screening 4strains with the ability of petroleum degradation from the soil contaminated by petroleum for a long time. One of them―Jc strain which had a higher petroleum degradation ability was chosen as a test strain and was studied on its degradation performance by 16 SrDNA sequencing. On that basis,the author chose the agricultural waste―walnut shell as carrier and used adsorption method to prepare the immobilized bacteria,thus an integrated research on the degradation performance of Jc strain was lunched by pH value,the mass concentration of petroleum hydrocarbon, the dosage of immobilized bacteria, the immobilized time of strain and so on. And the response surface methodology was adopted to optimize the degradation conditions and do some researches on the characteristics of its biodegradation kinetics. In the next place,the change characteristics of some factors of oxygen-releasing compounds(ORC)with different structural forms in aqueous solution were studied, including its oxygen-releasing speed,pH value,dissolved oxygen,ammonia nitrogen and total phosphorus.Finally,the microorganism-PRB system was formed through immobilizing the degradation bacteria of petroleum hydrocarbon in the packing medium―the waste(walnut shell).Conclusions as follows:Based on the 16 Sr DNA sequencing of Jc strain and homology comparison, it was obtained that Jc strain was Pseudomonas sp and its optimal growing time was 6~16h after the growth characteristic study on Jc strain.Additionally, optimizing the degradation conditions of immobilized bacteria by the response surface methodology,it showed the optimal conditions: pH value of 7.5,the mass concentration of petroleum hydrocarbon of 2735.55mg/L, the immobilized time of 28.79 h and the dosage of immobilized bacteria of 2.87 g. Under the above-mentioned conditions and7 days later,the degradation rate of this strain to petroleum hydrocarbon was up to 66.8%which was in close proximity to the experimental result―66.5% under the optimal conditions.Meanwhile, the second-order kinetic model had a better fitting effect on the degradationprocess of immobilized bacteria. It was obtained by significance analysis that the influence factors(from high to low) of microorganism on degradation rate of petroleum hydrocarbon were sorted as follows : pH value, the immobilized time, the mass concentration of petroleum hydrocarbon and the dosage of immobilized bacteria.The study on the oxygen-releasing speed of oxygen-releasing compounds(ORC) with different structural forms and the change characteristics of pH value,dissolved oxygen,ammonia nitrogen and total phosphorus in aqueous solution showed that bentonite bed and cementer layer in double-shell oxygen-releasing compounds had a better postponing effect on the reaction between CaO2 and H2 O along with a steady oxygen-releasing speed. Under the optimal conditions of solid-to-liquid ratio(1:40),the experiment result showed that the pH value was 8~8.5 and the dissolved oxygen maintained at a level of 8.5mg/L for a long time along with the ammonia nitrogen of 0.5mg/L and the total phosphorus of 0.06mg/L. The oxygen-releasing compounds(ORC) with double shell had a little impact on the water environment, which provided guarantee for groundwater in-situ remediation of microorganism under the aerobic or facultative conditions.At last, the degradation bacteria of petroleum was immobilized on the packing medium(walnut shell) in the strengthened PRB processing system in order to establish the microorganism-PRB system. Under the optimal vadose rate in PRB system,the experiment detected the change characteristics of pH value, dissolved oxygen and removal rate of petroleum hydrocarbon from various thief holes and water outlets. The experiment result indicated that when the optimal vadose rate was 6 mL/min,microorganism PRB technology had a better remediation effect on the groundwater contaminated by petroleum hydrocarbon and conformed to essential features of subsurface flow,which provided certain new ideas for the remediation of petroleum-contaminated groundwater.