Research On Preparation Of Composite Microorganism Agent And Its High-Efficiency Microbial Strains Degrading Btx

The activated sludge with high efficiency for the removal of benzene, toluene,and o-xylene(BTX) was inoculated on a specific carrier and enriched via a fermentation process.Thus,the composite microorganism agent applied for BTX degradation was successfully prepared.In the microorganism agent,the active organisms was more than 10⁹ CFU /g,and water content was less than 5%.The microorganism agent,instead of the acclimated activated sludge,could be employed for the start-up of the reactor to purify BTX without substantial loss of removal capacity.The effect of several operating parameters,including pH,drying temperature and the carrier proportion,on the performance of microorganism agent was investigated in detail.With an initial pH of 9.0,drying temperature of 35℃,and the carrier proportion of 85%:10%:5%,the best microorganism agent were obtained.Compared to the activated sludge,the microorganism agent has high stability,which could be stored for six months or more at 4℃.Four microbial strains capable of degrading BTEX were screened from the high-efficiency complex seeding sludge,which were named for Benzene 2-2,Toluene 3-1,Toluene 3-2,and H1-4,respectively.Basing on analysis of the Strains' morphological characteristics,physiological and biochemical characteristics,16S rDNA sequences and the Biolog identification,these four strains belonged to Microbacterium oxydans, Burkholderia cepacia,Mycobacterium cosmeticum,and Bacillus amyloliquefaciens respectively.These four strains were proposed as new species which can efficiently degrade BTX according to the relevant literatures.These four strains Benzene 2-2,Toluene 3-1,Toluene 3-2,and H1-4 could grow between 15-35℃with the optimum growth temperature of 30℃,and the optimum growth pH were 8,6,7,and 8 respectively.Strains growed well and BTEX could be degraded in 120h when the concentration of benzene,toluene,ethylbenzene,o-xylene were lower than 500mg/L, 300mg/L,l00mg/L and 125mg/L,respectively.These microbial strains could grow well and had higher removal efficiency for single substrate than for the BTEX mixtures.BTEX as substrates could be degraded by Strain Benzene 2-2,Toluene 3-1,Toluene 3-2,H1-4 in the following order: o-xylene＞ethylbenzene＞toluene>benzene,oxylene＞ethylbenzene＞benzen e＞toluene,o-xylene＞ethylbenzene＞benzene＞toluene,and oxylene＞ethyl benzene＞toluene＞benzene,respectively.The experimental results indicated these four strains could be successfully prepared for microorganism agent without substantial loss of removal capacity for BTX.Two positive mutant strains named as 1-1000-4 and 7-1000-1 were selected via an induction by ⁶⁰C_oγGamma rays for the original and wild-type strains.Compared to its original strain Benzene 2-2,strain 1-1000-4' removal capacities for BTX could be enhanced by 41.6%, 31.6%and 33%;while that of strain 7-1000-1 were enhanced by 70%, 31.4%,33.3%.,and these two strains have high passage stability, indicating their potential for the preparation of high-efficiency microbial agent.