| Phthalic acid esters(PAEs), As a kind of important chemical products additives,could increase the plasticity of the products,and it was widely used in plastic film,children's toys,cosmetics and other industries.It was not connected to products by covalent bond,so it was easier to release into the environment from products and pollute the environment.The main degradation way was microbial degradation in environment. Three bacteria strains MJ1, MJ2, MJ3, which could simultaneously utilize three kinds of phthalate acid esters(PAEs) DMP, DBP, DEHP as the sole source of carbon and energy, were isolated from soil in a refuse deposit in Zhenjiang.Strains were identified through morphology, physiology biochemistry and 16 S rDNA sequences analysis, and degradation characteristics of three strains for PAEs were tested. The results showed the strain MJ1, MJ2 and MJ3 was identified as Sphingobacterium sp., Bacillus sp. and Paracoccus sp. respectively. These three strains could degrade DMP, DBP and DEHP well, DMP and DBP could be degraded above 91%, and the removal rate of DEHP could also reach more than 82%. Three strains grew well with phthalic acid(PA), which was the intermediate product of PAEs degradation, as the sole carbon and energy source, and removal rate of TOC was higher, basically equal to the degradation rate of PAEs. It was illustrated that phthalates could be completely mineralized by the three strains through PA route.Multiple microorganisms were obtained by mixing three strains in a certain proportion. Influence of temperature, pH, concentration of substrate and amount of multiple microorganisms were investigated. The results showed that best degradation efficiency of PAEs by multiple microorganisms was obtained when MJ1, MJ2 and MJ3 were mixed in a proportion of 3:2:1. Temperature, pH, concentration of substrate and amount of multiple microorganisms had obvious effects on degradation of multiple microorganisms for PAEs. Under the conditions of temperature 30?, pH7.0,adding amount of bacteria 2%, removal rate of DMP, DBP, DEHP with initial concentration of 260 mg/L reached 97.62%, 94.29%, 92.55%, respectively. Compared with single bacterium, multiple microorganisms could shorten adaptive time and accelerate greatly the degradation speed of PAEs. And the time required to achieve identical removal is reduced by 72 h to 48 h.To obtain highly efficient microbial agents, the suspension of multiple microorganisms and salt medium were immobilized on the surface of the carrier, themixture of bamboo charcoal, birch sawdust and kieselguhr, and cultivated at 30? and then dried at 30?. Degradation efficiency of DMP, DBP and DEHP, stability and wide-adaptability of microbial agents were researched. The results showed that best preparation of microbial agents, which effective number of living bacterium was1.66?107 CFU/g, was obtained when the ratio of bamboo charcoal, birch sawdust and kieselguhr was 85%:10%:5%, cultivation time is 48 h and drying time is 4h. Microbial agents had higher biological activity. It could degrade 88.31% of DMP, 81.08% of DBP and 72.46% of DEHP within 3 days. Microbial agents could degrade 81% of DOP, 78% of DNOP, 62% of nonylphenol and 76% of o-nitrophenol, exhibiting broad spectrum. Microbial agents had good stability, Its biological activity was nearly unchanged after being preserved for 90 d at 4?.In order to investigate the feasibility for application of the microbial agents in treatment of sewage or waste water and bioremediation of water polluted by PAEs.Simulative PAEs sewage, prepared by adding PAEs into sewage, was treated by microbial agents. The results showed that microbial agents could adapt to the simulative sewage well, did not be devoured by native microorganism. Removal rate of PAEs in simulative PAEs sewage was the same as degradation rate of PAEs in PAEs solution. It is indicated that the microbial agents would had good application prospect. |
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