Isolation Of A Thermophilic Bacterium And Its Performance In Aerobic Composting Of Sludge

In recent years,the total amount of municipal sludge in China has increased rapidly,but most of them have not been properly disposed of.Aerobic composting technology has low cost and is suitable for small-scale treatment,and composting products can be reused by municipal green area.Therefore,aerobic composting technology has practical value in China.This study aims to isolate and purify thermophilic bacteria which can improve composting efficiency and accelerate composting process.Besides,this study also explores the feasibility and potential of sludge decomposing products used as fertilizers for municipal green area.The main research results are shown as follows:(1)A thermophilic strain P1 who could remain bioactivity at 70℃ was isolated and purified from the bacterial source sample.Through strain identification,this stain was identified as genus Bacillus.The optimum growth condition was temperature 50℃,pH 7.0,inoculum volume 3%,rotating speed 210 r/min.(2)In the small sludge composting test,the maximum temperature of the blank group(without added microbial agent)was 50℃,which did not meet harmlessness requirement as the temperature the groups with thermophile agents and the compound microbial agents exceeded 55℃,which met harmlessness requirement.Moreover,the highest moisture removal rate(8.83%)of the group with thermophile agent was better than that of the group with compound microbial agent(6.68%),indicating that the thermophile agent had better water removal effect,which was beneficial to sludge reduction.(3)By Using high-throughput sequencing methods,it was found that composting process reduced the richness and diversity of microbial communities in sludge.Of the blank group,the group with thermophile agent and the group with compound microbial agent,when aerobic composting process ended,the Alpha diversity index Chao1 decreased from 2073 to 1207,1377 and 1184;the ACE index reduced from 2227 to 1207,1470,and 1184.Besides,the proportion of actinomycetes increased significantly after composting treatment,from 4.6%initially to 32.8%,32.5%and 30.4%.According to hierarchical clustering analysis method of Beta diversity,the sample distances between the fresh sludge and the composting samples were larger than 0.339,and the sample distances between the composting samples with different microbial agents were less than 0.14.The smaller sample distance represents the higher similarity.This reflected that for the microbial community structure changes,composting stage affected more greatly than the type of microbial agents.(4)The application potential of composting maturity product used as fertilizers for landscaping area was analyzed from technology,economy and policy aspects.Most of the physical and chemical indicators of the composting maturity product met the requirements of related standard,but the moisture content was high and product needed to be dried for further application.This industry had huge market and made significant economic benefits.However,this industry still needed relevant policy support.