| Phthalic Acid Ester(PAEs)is the most widely used plasticizer in the plastic manufacturing industry,whereas dibutyl phthalate(DBP)is one of the most widely used PAEs in daily life.Because DBP has reproductive toxicity,neurotoxicity,teratogenic,carcinogenic and mutagenic toxicity,it can enter into the human bodies in a variety of ways,thus produce harm effect to people.As DBP can be detected in a variety of environmental medias,it has been given priority as the control pollutant by the environmental organizations in many countries.This study took dibutyl phthalate(DBP)as the target pollutant,and the DBP degrading strains DP-2,DP-5 and DP-6 as the bacterial sources.These strains were isolated from the activated sludge in a sewage treatment plant in Zhangjiakou,The strains DP-5 and DP-6 were identified based on 16S rDNA and morphological analysis,whereas DP-2 have been identified in the former research.The impact of environmental factors such as pH,temperature and rotating speed on the growth of the three strains were investigated.;To determine the relationships among the three strains,the antagonistic tests were conducted on strains DP-2,DP-5 and DP-6.The mixed bacteria DP3 was constructed based on the orthogonal test which optimized the mixing ratio of the three strains.T hen,the degradation characteristics and reaction kinetics of the mixed bacteria DP3 were further studied.An orthogonal test was conducted to investigate the immobilization conditions of DP3.In comparison with the blank pellets,the physical property and degradation ability of immobilized DP3 was verified by microbial activity test,and the degradation reaction kinetic test.The DBP removal performance in simulated artificial sewage of DP3 were further investigated.The main research results are as follows:(1)The 16S r DNA and colony morphology results showed that the strain DP-5 had the closest relationship with Acinetobacter bumannii,and the strain DP-5 was preliminarily identified as belonging to Acinetobacter.DP-6 had the closest relationship with Citrobacter freundii,and the strain DP-6 was preliminarily identified as belonging to Citrobacter,the strain DP-2 was preliminarily identified as belonging to Acinetobacter;(2)The impact of environmental factors such as pH,temperature and rotating speed on the three strains were as follows:they all showed some adaptability under weak acid and weak alkali environment.And they can grow normally in the range of pH 5?9?15?40? and rotating speed of shaking table 50?200 rpm.At 5?10? or pH 9,the bioaccumulation of strain DP-2 was significantly higher than that of the other two strains,When the rotating speed of the shaker is 0?100 rpm or the pH is 4,the result is opposite.and the adaptability of DP-2,DP-5 and DP-6 to the environment is different;(3)The best proportion of the DP-2?DP-5?DP-6 was 3:3:2.The constructed mixed bacteria DP3 has a high adaptability to the environment.It can degrade DBP under the condition of neutral alkali and strong acid.DP3 had a significant degradation effect on DBP,when the concentration of NaCl was 0?100 g·L-1,The degradation reaction of DP3 accords to the first-order kinetic process;(4)The best preparation conditions of immobilized DP3 were as follows:PVA 10%,SA 2%,AC 3%and CaCl2 1%.The DBP degradation rate of DP3 was 98.84%,35.11%higher than that of the free bacteria.The DBP degradation rate of DP3 can keep at more than 90%when cultivated at the condition of pH 4?10,NaCl concentration of 5?100 mg·L-1 and DBP concentration of 10?200 mg·L-1,which was significantly better than that of the free bacteria.At the same time,the DBP degradation rate can still reach to 99.95%after 20 times of degradation tests,without fragmentation.In addition,the DBP degradation rate in simulated wastewater of DP3 can reached up to 98.03%after 1 d cultivation.;(5)Compared with the free bacteria,the half-life of immobilized DP3 was Shorter.The degradation rate is obviously increased;... |
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