Study On Efficiency Of Aerobic Co-composting Penicillin Mycelial Dreg With Municipal Sludge

The disposal of microbial pharmaceutical residues is a bottleneck problem which restricts the development of the fermentation antibiotic production enterprises in our country.Although this kind of antibiotic residue contains a certain amount of drug residues,but its water content and organic matter content is higher,incineration treatment is faced with the high cost and the waste of resources.Aerobic composting is one of the economical and feasible methods to deal with this kind of bacteria residue,and the high temperature stage of composting process can strengthen the degradation of antibiotics residue.In this paper,as the study object with penicillin mycelial dreg?PMD?,the feasibility of composting PMD,the effect of different aeration rates and bulking agents on the process performance,the variations in dissolved organic matter?DOM?and its fluorescent components were investigated by means of aerobic composting,respectively.The changes of microbial population and enzyme activities in composting process and the diversity of microbial community structure were investigated by using the technique of flat plate culture and molecular biology.The degradation rate of penicillin G at different temperatures was investigated by batch tests.The results showed that the high temperature promoted the degradation of penicillin.In order to confirm the completed degradation of PMD during composting,the experimental-scale tests were firstly used to investigate the influence of different initial contents of penicillin G on the composting process and the degradation law of penicillin G with adding different levels of penicillin G,with the aims of providing technical support for disposing PMD in large scale composting in next step.The results showed that the composting process was not affected by the amount of penicillin G within the ranges of 30¹50 mg g^-1 for the addition of penicillin G,and penicillin G was completely degraded in the initial 7d.Both suitable aeration rate and suitable preparation of bulking agents?BAs?have the important significances in controlling conditions and optimizing the performance of composting process.The effects of three kinds of aeration rate(0.15,0.50 and 0.90 L min^-1 kg^-1 OM^-1)on composting PMD were investigated.The results showed that aeration rate affected the degradation of substates and pile temperature directly.Considering various factors fully,the aeration rate of 0.50 L min^-1 kg^-1 OM^-1 is a reasonable choice.The effects of seven preparations of BAs?consisting of three types: shavings,rice straw and sawdust conditioner?on composting PMD were conducted.The results showed that the peak maximum of temperature appeared in the pile added with sawdust,where the duration of high temperature stage continued for the longest time and nitrogen loss was relatively low.At the same time,the highest degradation rate of organic matter occurred using both rice straw and sawdust as bulking agents.Therefore,considering the factors such as temperature,nitrogen loss,the selection of rice straw and sawdust is suitable for composting PMD.Changes in DOM composition is more sensitive to reflect the maturation of composting than those in structure of solid components during composting process.The study on the variation in structure characteristics of DOM has important significance for characterizing the composting degree.The results showed that the compost increased the degree of aromatic structure of DOM and promoted the proportion of large molecular components through composting.In addition,three dimensional fluorescence spectra?EEM?intuitively displayed typical characteristics of fluorescence peak shift during composting.The results of fluorescence regional integration?FRI?for evaluating composting maturity showed that the values of PI,n?PII,n and PIV,n characterizing small molecules of aromatic of protein and microbial metabolites decreased,while PV,n characterizing humic substances increased remarkedly.Three-dimensional fluorescence spectroscopy coupled with parallel factor method?EEM-PARAFAC?was used to identify the numbers of fluorescent components,and then the relationships between fluorescent components of the DOM and the physicochemical indicators in the composting process were analyzed.Results showed that DOM contains five fluorescent components,C1,C2 and C3 associated with protein like substances,C4 and C5 representative of microbial source humic organic matter and terrestrial humic organic matter.The results of linear fitting among F_max of four components,DON,DOC,SOUR,and SUVA254 showed that the F_max of C4 was negatively correlated with SOUR and positively correlated with SUVA254,indicating that C4 had an important influence on the stability of composting of PMD.Dissolved organic carbon?DOC?was positively correlated with F_max of C3,but negatively correlated with the F_max of C5,which indicated that the protein contents of the feedstock are very high.It can be known from the changes of microbial population and microbial population structure that the number of bacteria and actinomycetes increased and then decreased,while the number of fungi decreased firstly and then increased.The number of bacteria was in the dominant position,followed by actinomycetes and fungi.The Shannon index of microbial diversity revealed that the diversity of microorganisms in the PMD pile is more abundant.In addition,compared to the control,the activities of catalase,phosphatase and cellulase were relatively high during the composting of PMD,while the sucrase activity was relatively low.Urease activity increased and tended to be stable,and its activity in the control was always relatively stable;the activity of protease in the two piles showed different trends.