| Organics are the most important pollutants with respect to pollution scale,species,and harm to human health and ecological environment.Since 60 s of 20 th century,all kinds of chemicals have accessed to markets.These chemicals caused serious pollution to groundwater and threaten human health.Since United States Environmental Protection Agency found organic pollutants in drinking water in 70 s of 20 th century,there are more than 765 kinds of organic pollutants in drinking water and 117 kinds of organics that have the property to cause carcinogenic effect,teratogenic effect,and mutagenicity.Researchers have studied the property and environmental behaviors of single organic pollutant in detail and obtained a lot of achievements.In fact,there is no single pollution existing in nature.Pollution often accompanies the associated and comprehensive character.It would be much more practical to study the remediation of complicated organics polluted groundwater.Meanwhile,there is a great progress in the bioremediation of organic pollutions,but the current researches only focus on the remediation of organics by a single kind of bacteria.Although pure culture technology helped researchers get rid of complicated situation in which several kinds of microbial existed and enriched our understanding of microbial genetic and physiological characters,researchers found that a great number of biological activities couldn't be done by the single kind of microbe.There were a lot of applications using consortium to degrade organic pollutants,but the researches mainly concentrated on the biodegradation of single pollutant,cellulose and petroleum.However,there were less applications of using consortium to degrade mixed organics in polluted groundwater.Due to the complexity of polluted groundwater in Jilin Petrochemicals,the single kind of microbe could not adapt the circumstances.Therefore,it is significant to screen consortium to degrade mixed organics under low temperature condition.There are some advantages of applying aerobic in-situ biobarrier to remediate organic polluted groundwater,such as the low cost of running and maintenance,environmentally friendly,suitable for the low concentration organic polluted groundwater,and the complete removal effect for pollutants.However,the current oxygen supplying system has some shortcomings,such as high cost of running,low efficiency,and effecting aquifer's permeability by forming bubble.Thus,it is necessary to develop an advanced oxygen supplying system which has the following characteristics: low running cost,saving raw material,high efficiency,and low impact on aquifer's permeability.The closed circle oxygen supplying system combining with the high porosity filling used in this thesis can tackle these problems.The target of this study was polluted groundwater in Jilin Petrochemicals.Objective contaminants were established as nitrobenzene,aniline and BTEX according to the results of site samples' analysis.The disadvantages of nitrobenzene and aniline analysis methods were analyzed,and a new analysis method was established.Moreover,two consortia were screened to degrade nitrobenzene-aniline and BTEX and their degradation characteristics were studied.In addition,the mixed consortia with high efficient degradation rate were constructed for polluted groundwater in Jilin Petrochemicals and their degradation characteristics were studied.In this paper,a suitable oxygen supplying system was designed and used in the in-situ biobarrier which was applied to remediate polluted groundwater;the mixed consortia's stability and removal effect on the contaminants were investigated.It turned out that the boibarrier had a very good removal effect on the contaminants.Therefore,the results of this research might be helpful for our country's mixed organics polluted groundwater.There were three main results in this paper,as follows:1 Site's pollution background analysis and establishment of nitrobenzene-aniline analytical method:1)According to analytical results of site groundwater,the groundwater had the following properties,such as high salt content,low temperature,various types of organics,complex structure of organics,high concentration of pollutants,and variable space distribution of organics.The main pollutants were nibrobenzenes,phenyl amines and BTEX.The concentrations of nitrobenzene,aniline,benzene and toluene in the No.0 well were 439.38,46.26,115.76,5.23 mg/L,respectively.The concentrations of nitrobenzene,aniline,benzene and toluene in the No.2 well were 194.4,92.72,104.3,4.86 mg/L,respectively.Therefore,the objective pollutants established for next step experiments were nitrobenzene,aniline,and BTEX.2)Microbial characteristics of the site showed that there were no aerobic bacteria in the groundwater;however microbial which could degrade nitrobenzene,aniline and BTEX existed;the amount of the microbe in the site was less than control sample;microbial activity in the site was similar with the control sample.3)This research studied a fast and direct method to measure aniline and nitrobenzene of water sample by High Performance Liquid Chromatography.The operation condition was as follows: injection volume was 5?L,flow rate was 1m L/min,mobile phase was V(acetonitrile):V(ammonium acetate 3.85 g/L + acetic acid 3 g/L)=65:35.Aniline was analyzed by fluorescence,?ex/?em =280 nm/340 nm;nitrobenzene was analyzed by ultraviolet,the wavelength is 262 nm.The separation column was Eclipse XDB2-C8(4.6mm×150mm,5?m),test time was 3.2mins.Samples' pretreatment method: first,mixed thoroughly 1m L water sample and 1m L methanol;second,filter the mixture through microfiltration membrane(O).Moreover,the linear correlation coefficients of aniline and nitrobenzene standard curves were greater than 0.999.The relative standard deviation of eight parallel injections was smaller than 2%.Recovery rate of the method was between 89%-110%.The superior detection limits of aniline and nitrobenzene were 50 mg/L and 200 mg/L respectively.The method detection limit of aniline and nitrobenzene were 17.59 ?g/L and 20.80 ?g/L,respectively.2 Screening of nitrobenzene-aniline and BTEX degrading consortia and construction of mixed consortia degrading the mixed pollutants:1)Nitrobenzene-aniline and BTEX degrading consortia were screened from the soil in Jilin Petrochemicals and activated sludge of Jilin Petrochemicals wastewater treatment factory.Removal rates of BTEX by BTEX degrading consortium were greater than 88%.Removal rates of nitrobenzene and aniline by nitrobenzene-aniline degrading consortium were both greater than 95%.There were 8 culture bacteria and 5 culture bacteria in nitrobenzene-aniline consortium and BTEX consortium,respectively.2)According to BIOLOG bacteria identification system and 16 s r DNA technology,BTEX degrading bacteria were Stenotrophomonas maltophilia,Pseudomonas maculicola,Pseudomonas spinosa(Burkholderia);nitrobenzene degrading bacteria was Pseudomonas corrugate;aniline degrading bacteria was Pseudomonas fluorescens,.3)The degradation range of BTEX degraded by its degrading consortium was between 25 and 200 mg/L,and the degrading range is relatively wide.The removal rate of BTEX was still greater than 95% even after 80 times' passages.The degrading ranges of nitrobenzene and aniline degraded by their degrading consortium were both between 0.7 and 550 mg/L The removal rate of BTEX was still greater than 98% even after 80 times' passage.4)The degradation mechanism of nitrobenzene and aniline was studied in this paper.The degradation mechanism of nitrobenzene followed the same pathway which was published already.The proposed aniline's degradation mechanism seemed follow a new pathway according to stoichiometry.5)The analysis of degrading byproducts of nitrobenzene and aniline under different concentrations showed that there were many byproducts when the total concentration of nitrobenzene and aniline was more than 300 mg/L;however,there was no byproduct when total concentration of nitrobenzene and aniline was less than 100 mg/L.Moreover,there were byproducts when there was only aniline in solution.There were some byproducts when there was only nitrobenzene and its concentration was less than 10 mg/L.Nonetheless,there were no byproducts when nitrobenzene's concentration was more than 100 mg/L.Therefore,the optical degrading range for nitrobenzene and aniline was between 10 mg/L and 100 mg/L.6)The optical applicable mixing ratio of nitrobenzene-aniline degrading consortium and BTEX degrading consortium was established.The removal rates of nitrobenzene,aniline,benzene and toluene were all greater than 95%.However,the removal effect of pollutants in raw water varied under different dilution factors.The removal rates of nitrobenzene,aniline and benzene were greater than 95% under 5 times dilution at the 6th day;the removal rates were greater than 95% under 3 times dilution at the 7th day;the removal effects were poor or there was no degradation under 1,10 and 20 times dilution.7)The mixed organic pollutants degrading consortia could adapt to different p H from 5 to 9,but they needed much oxygen to perform well.The mixed organic pollutants degrading consortia could degrade pollutants under the temperature from 8 to 30 ?and under different chemical conditions,but the adaptation of BTEX degrading consortia was poor.8)Full scan analysis of byproducts under different conditions in shaking flask experiments showed that all the organics could not be fully degraded and there were some nitrobenzene compounds and phenyl amines left.3.Research on remediation of the contaminated groundwater using in situ bio-reactive barrier:1)The absorption experiment' results showed that the filler which was mixed with perlite and peat soil(4:1 by volume)performed a very good absorption and immobilization effect on the degrading consortia;Moreover,the filler would not affect the consortia's degradation on aniline,nitrobenzene,and benzene,and the peat soil would not degrade naturally.2)The results of column experiment on the organic contaminants' transformation illustrated that the filler had relatively high absorption ability on both nitrobenzene and aniline;moreover,the filler had higher absorption ability on nitrobenzene than that on aniline.After 335 hrs(7.5 pore volume water)of the column experiment,the concentration of nitrobenzene in the effluent was only about half concentration in the influent.After 384 hrs,organic contaminants broke through in succession in the following order: aniline,phenyl amines,nitrobenzene,and nitrobenzene compounds.3)The control bio-reactive barrier experiment's results indicated that the concentrations of aniline,nitrobenzene,and benzene increased with the time went on.When it was 19 days,only the aniline's concentration in the effluent almost approached the influent's concentration.Meanwhile,the organic contaminants' full scan analysis indicated that all the organic contaminants broke through the column.4)The results of oxygen dispersion experiment in the closed circulating oxygen supply system showed that the oxygen's dispersion was very fast,and the oxygen's dispersion coefficient was 1.46×10-3 m2/s.After 9 hours' aeration,the concentrations of dissolved oxygen(DO)for all the sampling points are all more than 8 mg/L.As soon as the closed circulating oxygen supply system was applied to the biobarrier,the concentrations of DO in the front and back boundaries were kept between 1mg/L and 2mg/L,and the concentration of DO near the two rows' aeration wells in the biobarrier was more than 4 mg/L which could provide enough dissolved oxygen for the consortia to degrade contaminants.5)The results of the bio-reactive barrier experiment indicated that nitrobenzene,aniline,and benzene could not be detected in the effluent during the 156 days operating time;moreover,according to the full scan analysis,no other organic contaminants detected in the effluent illustrated that the biobarrier could remove the contaminants which could not be degraded in the shake flask experiment.The monitoring results of the hydraulic head difference between the bio-reactive barrier's front and back sides showed that the hydraulic head difference increased with time went on;however,due to the filler's high porosity characteristic,the block problem was not found in the overall experiment.6)The metabolic functional diversity analysis of the consortia used in the biobarrier and the microbial community existed in the final phase of the experiment showed that the activity of consortia in the biobarrier was higher than inoculated consortia.Diversity indexes of microbial function showed that the richness of every consortium was similar,but evenness and the most common species were different.According to principle component analysis of consortia using carbon,consortia in the filler had high similarity,but the BTEX degrading consortium,the consortium in the 1st well and other consortia were different.After running 150 days,the carbon utilization fingerprints of consortium in filler and incubated consortium were similar.This showed the mixed organics degrading consortia was very stable.The biobarrier ran for 156 days.Total influent volume was 1601 L.There were 21.35±1.00 g,51.23±1.30 g,and 17.08±0.80 g of aniline,nitrobenzene and benzene removed,respectively.Meanwhile,large amounts of phenyl amines,nitrobenzene compounds and other organics were removed.Thus,the biobarrier combined with the closed circulating oxygen supply system could remediate groundwater polluted by various,complex and high concentration orgaics.The innovations of this work were as followed:(1)High Performance Liquid Chromatography was used to determine the concentrations of aniline and nitrobenzene in water through direct injection simultaneously.The detectors of nitrobenzene and aniline were UV detector and fluorescence detector respectively.Compared with the standard method,there were some advantages of this method,such as simple pretreatment and less pollution to environment.(2)Complex organics degrading consortium was screened under low temperature.The consortium contained nitrobenzene,aniline and BTEX degrading bacteria and others.Batch and applying biobarrier experiments showed that the consortium could degrade the complex organics fast and effectively and it was very stable.This paper results could provide a good degrading consortium for following biotechnology engineering.(3)The closed circulating oxygen supply system was designed.Simulation experiment showed that this technology was economic,effective and low impact on groundwater flow.Moreover,the closed circulating oxygen supply system could provide enough oxygen for consortia in the biobarrier and necessary condition for successful biobarrier implement.The paper's achievement could provide technical reference and theoretical foundation for demonstration project. |
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