Acclimating,Isolating Aerobic Degradation Strain Capable Of Pbdes-degradingand The Study Of Degradation Characteristics

Polybrominated diphenyl ethers(PBDEs)is a kind of widely used brominated flame retardants.As a class of environmental persistent organic pollutants generally existed,the degradation research of PBDEs has aroused concern of domestic and foreign scholars.The toxicology effects,environmental behavior and distribution,transportation and transformation of PBDEs has become a hot research topic.In this paper,decabromodiphenyl ether(Deca-BDE)as a most representative PBDEs and difficult to aerobic microbial degradation was selected as research subject to make a study of microbial degradation.In this study,the aerobic degradation strain capable of PBDEs-degrading was screened from environment and identified on the basis of that Deca-BDE was determined through the HPLC-UV method.The degradation efficiency of PBDEs was analyzed through optimizing strain's growth and degradation conditions,simulating degradation kinetics of Deca-BDE,and tring synergistic degradation with microorganism and MZVI.Meantime,strain's degradation characteristics and the optimal degradation method were discussed.The main conclusions in this paper were as follows:(1)The strain GH10 can grow well using Deca-BDE as the only carbon source,and the Deca-BDE of aqueous samples can be determined through the HPLC-UV method.The specific chromatography condition were as follows:the chromatographic column was Inertsil ODS-3 C18(5 um,250 mm × 4.6 mm),the detection wavelength was 260 nm,the column temperature was 30?,the mobile phase was V(acetonitrile)/V(water)=95:5,the flow rate was 1.2 mL/min,the sample volume was 20 uL,the sampling method was manual injection.(2)An aerobic bacterial strain capable of PBDEs-degrading was isolated from activated sludge from sewage treatment plant.The strain GH10's individual was micro rod,mucus layer wrapped around the cells,colony was round,neat edge,yellow,smooth,moist,convex,gram stain was positive.The strain of the bacterium was identified as Leifsonia shinshuensis through analyzing morphological character,physiological and biochemical characters,16S rDNA sequence and phylogenetic tree.(3)The sequence of the effects of temperature,pH,shaking speed on the growth of strain GH10 was:pH>temperature>shaking speed.The optimal growth condition of strain GH10 was temperature at 30?,pH at 7.0,shaking speed at 150 r/min.In the whole growth period of strain GH10,strain GH10 reached logarithmic period on the second day(48 h),then changed to stable period on the third day(72 h),finally entered the decline period on the fifth day(128 h).(4)Optimal initial experimental concentration of strain GH10 for Deca-BDE degradation was 50 mg/L.Degradation conditions of strain GH10 were temperature at 30 ?,pH at 7.0,inoculum rate at 10%.When the bacterial suspension of strain GH10 was inoculated according to the inoculum rate 10%into the inorganic salt basal medium of Deca-BDE concentration 50 mg/L,the degradation rate of Deca-BDE reached 59.24%with dark culture for 5 days in the conditions of temperature at 30?,shaking speed at 150 r/min.Adding external carbon source glucose can improve the degradation rate of Deca-BDE to 90.08%under the same conditions.It was found that adding external carbon source glucose can decrease the half-life of Deca-BDE from 3.91 days to 1.45 days.(5)The pickling treatment for MZVI was beneficial to the debromination reaction before the experiment.Reaction conditions of acidic,high temperature,Deca-BDE initial concentration and iron powder dosage,the smaller iron powder size were more conducive to MZVI debromination reaction.If the carbon source was abundant,strain GH10 could have grew in the environment that MZVI concentration was less than 2.5 g/L.Using the degradation method of MZVI and strain GH10 continuous degradation to degrade Deca-BDE,the degradation rate can reach 91.46%after 5 days.This degradation method was better than other methods,and can shorten the half-life of Deca-BDE to 1.36 days.(6)Using MZVI of pickling recovery after reaction with microorganism to make debromination reaction can achieve analogous debromination effect with new pickling MZVI to make debromination experiment after 5 days.To sum up,Leifsonia shinshuensis screened from activated sludge can use Deca-BDE as carbon source to grow well and has a good degradation effect on Deca-BDE in the conditions of temperature at 30?,pH at 7.0,inoculum rate at 10%.Adding external carbon source glucose can promote the degradation of Deca-BDE.At the same time,using the degradation method of microorganism and MZVI continuous degradation to degrade Deca-BDE can achieve the desired result,and effectively shorten the half-life of Deca-BDE.