Study On Immobilized Microorganisms Remediate Chlorobenzene-contaminated Groundwater

Chlorobenzene is a synthetic organic compounds. It is widely used in industrialand agricultural production. It is difficult to be degraded by indigenousmicroorganisms in the groundwater environment. Using the traditional biologicaltechnology to inject high-degrading bacteria can improve the degradation efficiency.But the degradation effect is not very ideal. Because microorganisms lost a lotthrough soil porous media. Immobilization microbial technology is widely used inwater treatment in recent years. Microorganism is immobilized in polymeric gel. Itforms an isolated environment for microorganism. The activity of microorganism andthe efficiency of pollutants degradation are improved. The effect of bioaugmentationis enhanced.This study based on groundwater characteristics，select the better suitable gelfor remediation chlorobenzene contaminated ground water and improve it. Apply thegel to the dynamic soil column experiments. Through this study got the followingresults：（1）The strain was screened for high degradable abilities. By the bacteriamorphology and colony characteristics, staining and recessive reaction,the stain isidentified as Pseudomonas sp. Based on the growth of chlorobenzene degradingbacteria, the strain could grow well at low temperatures, and use chlorobenzene assole carbon source for growth and reproduction.（2）Using static factors-choosing experiment,the optimal conditions for sodiumalginate embedding method immobilizing chlorobenzene degrading bacteria:SAconcentration of60g/L,CaCl₂concentration of30g/L,NaCl concentration of20g/L,the embedding medium and the broth volume ratio of2:1. The optimal conditions forpolyvinyl alcohol embedding method immobilizing chlorobenzene degrading bacteria:PVA concentration of80g/L，CaCl₂concentration of10g/L, NaCl concentrationof15g/L,the embedding medium and the broth volume ratio of30:1，SA massfraction of1.0%.Make two kinds of the gel in the best conditions and study therelationship between the gel size and chlorobenzene degradation. The results show the smaller the size of gel, the greater the chlorobenzene degradation rate. The studyselect the minimum size （0.5mm） gel that could make in experimental conditions.Compare two kinds of the gel with the chlorobenzene degradation rate andperformance （operation, transitivity, mechanical strength, swelling）.The results showthat the SA gel chlorobenzene degradation rate of86.75%is higher than the PVA gelof80.11%.The operation and transitivity of the SA gel are better than that of the PVAgel. The swelling degree of the SA gel is less than the PVA gel. Above all results, thesodium alginate is the better carrier.But the swelling degree of the SA gel is so large,itshould be improved to be applied in groundwater pollution.（3）Impact of pH and the quality concentration of chitosan acetate solution, andcoated time on the transitivity and swelling degree of the gel. Considering the effectof the two performances on the soil column experiments, it determines that theoptimal concentration and pH of chitosan acetate solution, and coated timeare:0.8%,5.2,10min.（4）In dynamic soil column experiments, study on the concentration of gel changewith time in different size of the aquifer medium.The results showed that the smallerthe particle size of the aquifer medium, the more difficult gel to migrate, the slowerthe migration. The concentration of gel increases over time in different regions of thesoil column. But the injecting concentration of gel affect the migration capacity of gel,causing gel migration to be blocked. So the concentration in some region reducessuddenly. When the injection concentration more than0.68g/L,it will cause themigration of the gel blocked in A column（2-5mm）. When the injection concentrationbetween0.50g/L and0.68g/L, it is more conducive to the migration of the gel. Themigration of the gel in B column（1-2mm）is slow in the aquifer media, the migrationof the gel does not change with the injection concentration. Compare the remainpercentage of the gel in different groundwater velocity, it determines that the fastergroundwater flows, the more conducive to the migration of the gel in the aquifermedia. By comparing different sampling ports with chlorobenzene degradation.Theresults showed that the better migration in the aquifer media, the better chlorobenzenedegradation. By comparing the chlorobenzene degradation of immobilized microorganisms with that of ree microorganisms, it concludes that the immobilizedmicroorganisms have the faster ability to adapt to the environment, can removechlorobenzene well in a short time. The degradation of immobilized microorganismsis better than free microorganisms.