Effect Of Temperature On Characteristics Of Microbial Community During Vermicomposting Of Pelltetized Dewatered Sludge

Vermicomposting involves the interaction of earthworms and microorganisms to degrade the organic matter in the substrate,which is made the humification,stabilization and the harmlessness of pathogenic bacteria and finally reached the metabolic process.The degradation and transformation of organic matter mainly depend on a variety of microorganisms(bacteria,actinomycetes,fungi,protozoa,metazoan and microfauna,etc.)Different microbial groups in composting process independently or cooperatively decomposes a differential organic matter,and earthworm plays an important role in nitrogen transformation,the decomposition of cellulose and humification,and earthworms can affect the biochemical properties of sludge.It has been found that the addition of earthworms reduces the amount of microorganisms,including bacteria and fungi,and accelerates the decomposition of organic matter.Previous studies have shown that the treatment of sewage sludge by earthworms can accelerate the degradation process of organic matter,and contain the lower values of microbial biomass carbon(MBC)and dehydrogenase activity(DHA)in the earthworms group;combined with the technique of PCR-DGGE in analysing the changes of microbial community structure in the process of making sewage sludge stabilization by earthworm PCR-DGGE images showed the diversities of bacterial and fungal communities have a slightly changes in earthworms group.However the DGGE fingerprint only reflects more than 1% of microflora,Miseq high-throughput sequencing technology is used to analyse microbial community structure and succession.The date was based on Miseq high-throughput sequencing technology study the effect of earthworms on the microbial community in the decomposition treatment of pelltetized dewatered sludge,and the effect of temperature on characteristics of microbial community during vermicomposting of pelltetized dewatered sludge.The physicochemical properties of vermicomposting of pelltetized dewatered sludge,microbial community structure and the relationship between microbial community structure and environmental factors are shown as follows:(1)microbial diversity fluctuated during the vermicomposting.Except for 30 th and 60 th days,the richness and diversity of bacterial community were different in earthworm and control groups;From the 10 th to 40 th days,the fungi community diversity in the earthworm group was higher than in the control group,and result are opposite form 50 th to 60 th days,so the addition of earthworm will affect microbial community diversity in the stabilization process of pelltetized dewatered sludge.(2)The microbial community structure of the initial sludge were significantly different with other samples;The structure of the bacterial community are similar in the earthworm group and the control group,but the structure of the fungal community was different.The effect of earthworms on the bacterial commnity was less than that of the fungal commnity,which may be related to the number and type of bacterial community.The dominant bacterial community in the earthworm group of sewage sludge were Sphingobacteriia,Betaproteobacteria,Gammaproteobacteria,Actinobacteria,Alphaproteobacteria,Flavobacteriia,Deltaproteobacteria,Bacteroidia,Anaerolineae,Clostridia,Bacteroidetes_vadinHA17,Cytophagia,and Caldilineae for 84.94% ~92.03%.The dominant fungi community were Tremellomycetes,Zygomycota_incertae_sedis,Fungi_incertae_sedis,Ascomycota_norank,Pezizomycetes,Saccharomycetes,Cryptomycota_norank,Fonticulidae,Sordariomycetes,Ascomycota_unclassified,Fungi_unclassified,and LKM15_norank.(3)RDA was used to analyze the relationship between microbial community structure and environmental factors(DOC,NH4+-N,EC,pH).The results showed that dissolved organic carbon and ammonium nitrogen were the main factors affecting the microbial community structure of vermicomposting.There was a good correlation between the dominant microbial community and environmental factors in the process of stabilization of pelltetized dewatered sludge by earthworm.(4)The Shannon index of the bacterial community in the three temperature groups had slight difference during vermicomposting,and the higher the temperature,the lower the richness of the bacterial commnity in the treatment of sewage sludge samples.The species diversity index between the three temperature groups had a lot of differences except for 30 th day,and at the end of the experiment the diversity index of 20? group was higher than 15? and 25? groups.(5)The composition of the dominant bacterial community was similar between 15 ? and 20 ?,but was different with the 25 ? group.The fungal community structure vary greatly in the three groups,and the temperature affected more the fungal community structure than the bacterial community in vermicomposting.The dominant bacteria in three group were Sphingobacteriia,Betaproteobacteria,Gammaproteobacteria,Actinobacteria,Alphaproteobacteria,Flavobacteriia,Deltaproteobacteria,Bacteroidia,and Clostridia,accounting from 75.89% to 89.71%.These bacterial are related to the degradation of organic carbon and organic nitrogen.The dominant fungi in three group were Tremellomycetes,Zygomycota_incertae_sedis,Saccharomycetes,Ascomycota_norank,Pezizomycetes,Fungi_incertae_sedis,accounting from 59.23% to 93.21%.(6)RDA was used to analyse the effect of temperature on the microbial community during vermicomposting of sewage sluge showed that the microbial community structure and environmental factors(DOC,NH4+-N,EC,pH,T)had a good correlation.The results showed that the main environmental factors affecting the bacterial community structure were DOC and EC;The main environmental factors affecting fungal community structure were DOC and temperature.