Research On The Remediation Of Chemical And Biological Reactive Barrier In Ground-water Nitrobenzene,Aniline Contaminant

Recently, all kinds of organic compounds, heavy metal and radioactive waste have been put into environment due to rapid development of petroleum chemical industry, irrational bury of industry and agriculture waste, accident discharge of pollutant and equipment leakage of oil store. This gives rise to heavy pollution for both surface water and underground water as well as soil. Because of hidden characteristic and irreversibility, the pollution of underground waste is difficult to reduce and control. So protecting underground water and eliminating organic compound pollutant have been an imperative task of environmental protection.This paper mainly researches reaction mechanism of nitrobenzene under the function of zero valence ferrite, selecting the bacteria of rapid degradation for nitrobenzene and aniline under low temperature and researching degradation mechanism by investigating nitrobenzene discharge of Jilin chemistry factory explosion in November 2005. At the same time, the pervious condition restoration technique and method have been tested by designing chemical and biological reaction wall and imitating explosion scene under the combining PRB technique condition. The result of the paper possesses theoretical and practical implication.1. The imitating test result of underground water polluted by nitrobenzene was dealt with chemical reaction wallThe reaction mechanism of nitrobenzene with is reducing function the mainly production is aniline which can be degraded biologically and the order of reaction is second order reaction. In dealing with nitrobenzene waste water, the major factors include: pH value of experimental water, stop time, gas flux, concentration of nitrobenzene, reaction temperature, ratio of Fe:C, particle diameter of iron fillings. The experimental result manifested that the eliminating nitrobenzene effect which is difficult to degradation by Fe is comparative good on under the ambient temperature and acid property condition. The iron filling diameter selected is between 0.1 mm and 0.2 mm. Controlling Fe:C=5:1 and passing appropriate oxygen gas. When the reaction time is 60 min, the reduction rate of nitrobenzene reaches 83.1% and when the reaction time is 120 min the reaction rate can reach 97.4%.2. Selection and culture experiment of nitrobenzene degradation bacteria and degradation characteristicBy concentration culture four bacteria which can rapidly degrade nitrobenzene and phenyl amine under the low temperature condition were selected form bottom slurry of discharge exit of Factory.(1) Pseudomonas asplenii which can degrade effectively under sufficient oxygen gas condition was obtained by sieve and culture. In the course of culture the growth of nitrobenzene bacteria in early stage needs additional inorganic nitrogen. The generation time calculated was 12.11 hours by growth curve of nitrobenzene bacteria.(2)Higher degradation rate was obtained when inoculation capacity of initial bacteria solution is from 3 to 10 ml in 100 ml cultural solution. Primary bacteria concentration is from 7.3×1017 to 2.44×1018 one/ ml. glucose as additional carbon resource, KNO3 and Mg2O2 as election receptor.(3)The growth condition of nitrobenzene bacteria was defined as pH=4.0～9.5, T=15~35℃. CNH4Cl>0.1%,C0=50-250.The optimum growth condition under laboratory is pH=7.0, T=35℃, C0=150-250,endure concentration degradation for nitrobenzene reaches 1500, which shows a strong activity and ability.(4)The kinetic model of Pseudomonas asplenii growth was certain as The kinetic model of nitrobenzene degradation as3. The experimental result on the sieve and culture and degradation characteristic of aniline degradation bacteria.The aniline degradation bacteria can metabolize in the condition of aniline as the only nitrogen resource and can degrade aniline at love-oxygen and anaerobic condition. The degradation rate at love-oxygen condition is higher a little than that at anaerobic condition. The optimum temperature of degradation phenyl amine is 37℃, pH=6.5-8.0, endure concentration of phenyl amine is 4000, suitable initial concentration is 500-2000, aniline degradation is in according to second order reaction kinetic model. Hg2+ and Ag+ existed a repression function for degradation to some extent.This is different from most aniline bacteria which needs love-oxygen environment, suitable pH value range. This bacteria has an appropriate-environmental ability. It can provide more options for match between microorganism and technology. It is suitable to application of biological system and polluted environment.4. The experimental result of biological reaction wall(1)The particle size 0.5-1 mm active carbon was selected as absorption support. The fixing rate reached above 90% and the optimum degradation of fixing bacteria is pH=6-7.(2)Biological reaction wall was produced with microorganism fixed by active carbon, which possesses excellent elimination for target pollutant. The 30 days run result of biological reaction wall shows that the degradation rate can reach above 98.83% for the primary contraction nitrobenzene as 300.89 and degradation rate reaches 99.63% within 71 days. For aniline which primary concentration is 87.35 , the degradation rate reaches above 96.44% in 36 days and the degradation rate can reach 99.61% in 71 days.(3)Degradation mechanism of nitrobenzene is decided into two ways-oxidized destructive metabolism and reduces destructive metabolism, i.e., anaerobic reduction as aniline and love-oxygen degradation as inorganic compound.The degradation mechanism of aniline conducted by two metabolism processes—ortho—and meta—metabolism. Hydrogen peroxide enzyme is added into ortho—phenylene diphenol 1,2 or ortho—phenylene diphenol 2,3 respectively.5. Restoration underground water model experiment result of combination chemistry and biology reaction wall.(1)Fe0 possesses a strong reduction function, it can reduce nitrobenzene into aniline but the underground water can not conform to the drinking standard, because the aniline was not eliminated completely. Combining with biological reaction wall, the processes effect can reach for organic pollutant in underground water. The water flow capacity in the le experimental process is 5.70L/d, level flow rate is 6.4cm/d, pH=5.6-8.0. Eliminating ratio of nitrobenzene and aniline can reach 99.91% and 99.95%.(2)The problem in application of chemical and biological reaction wall can not be ignored. The phenomena such as the growth of Fe3+, the growth, death and chemical deposition can block the reaction equipment, affect the service life of PRB technique, shorten the replace periodic of reaction media. These factors are unfavorable for application of PRB technique. Therefore, the necessary measure was adopted according to the condition of underwater pollutant. For example, other metal such as Ni, Pd, Zn, are added into chemical reaction wall which can produce catalysis function, enhance reaction activity of Fe0 and block producing oxidized film and deposition. (3)Recently, the sieve of reaction media for PRB technique is still limited in water process materials, especially colloidal. So it is necessary to extend the range of sieve according to underground water quality and environmental condition and promote the further development of PRB technique.