Study On Component Change And Microbiological Mechanisms Of Storage Sludge During Biodrying Process

In recent years,with the increase of sludge production,more and more attention has been paid to the problems caused by storage sludge.Therefore,it is urgent to treat storage sludge.However,the properties and high water content of storage sludge affect its further treatment and disposal.Hence,the analysis of the properties of storage sludge and drying are the key to subsequent treatment.Biodrying is one of the economical and feasible methods to treat storage sludge.In this paper,the properties of storage sludge during long-term storage process were analyzed.On this basis,the key influencing factors of storage sludge biodrying were studied,and the prediction model was established.The transformation r ules of different components as well as changes in water and heat during the biodrying process were studied.Finally,the community structure and functional characteristics of microorganisms during the biodrying process were explored by molecular biology technology,and the relationship between water change and microbial community was revealed.The properties of storage sludge could affect the subsequent treatment and disposal methods,and its properties could change during the long-term storage process.Therefore,the change of storage sludge properties with storage time in a sludge landfill site in Shenyang was analyzed,and the relevant mathematical models were fitted.The results showed that the moisture content of storage sludge was always maintained at a high level?75⁸0%?in the long-term storage process.The content of organic matter gradually decreased,the decline trend was obvious in the early stage,and gradually slowed down in the later stage,eventually dropping to about 38.45%.Additionally,the contents and speciation of heavy metals such as Cu,Zn,Cr,Ni,Cd,As and Hg did not change significantly.The variation trends of total nitrogen,NH₄⁺-N and NO₃^--N were better fitted with Gauss function,Fourier function and Polynomial function,respectively.Bulking agent and ventilation have important influence on the biodrying of storage sludge.Therefore,the key influencing factors,such as bulking agents type,bulking agents ratio,ventilation mode and ventilation rate were investigated.The results showed that the ratio of storage sludge to beer lees was 5:1?w/w,wet weight?,the ventilation mode was intermittent ventilation with 10 min on/20 min off and the ventilation rate was 1.4 L min^-1 kg^-1 DM was a more appropriate choice and the moisture content decreased from 70.90%to 56.36%.Furthermore,the prediction model based on support vector regression machine could accurately predict the change of moisture content during the biodrying process.Changes in water-soluble organic matter,humus and different elements indicated that biodrying could promote the transformation of materials to stable macromolecular substances.The degradation of different components of organic matter?water-soluble components,cellulose,hemicellulose and lignin?showed that the degradation of organic components with different structures was different in the progress of biodrying.The analysis of water balance showed that evaporation was the main way to remove water,accounting for more than 90%of the total water removal.Thermal analysis showed that evaporation was the main way of heat loss,accounting for about 60%of the total heat consumption.The contribution of bulking agents to the bio-heat of biodrying system was more than80%,which was much higher than that of storage sludge.Therefore,it is very necessary to add bulking agents during the biodrying of storage sludge.The plate counting method was used to investigate the changes in the number of microorganisms during biodrying process.The results showed that the number of bacteria changed similarly to actinomycetes,which increased first and then decreased.The number of fungi increased slightly in the early stage,and then declined rapidly.The different enzyme activities in the process of biodrying were analyzed.The results showed that the activities of amylase,protease and lipase increased first and then decreased.Lignocellulase?xylanase,carboxymethyl cellulose,and lignin peroxidase?remained at a low level throughout the biodrying process.The community structure of microorganisms?bacteria and fungi?during biodrying were investigated by high-throughput sequencing.The results of bacterial community showed that the biodrying process could lead to the decrease of bacterial community diversity and the dynamic change of community structure.The dominant genera in thermophilic period were Ureibacillus and Bacillus.According to the functional analysis of bacterial communities by PICURSt,the main biochemical metabolic pathways were metabolism,genetic information processing,environmental information processing and cellular processes.The analysis of fungal community also showed that the diversity of fungal community decreased after thermophilic period.At the genus level,the dominant fungus was Pichia in thermophilic period.The functional analysis of fungi using the FUNGuild database showed that fungi were mainly classified into pathotroph and saprotroph according to the trophic mode.The relationship between water change and microbial community showed that Bacillus,Ureibacillus and Pichia played an important role in water evaporation during biodrying process.