| In the present study,agricultural wastes of rice straw and pig manure,which were pretreated by a previously constructed cellulolytic microbial consortium,were regarded as research substrates.By studying the environmental factors?carbon to nitrogen ratio,feed to water ratio,oxidation-reduction potential?which affect the bio-degradation of rice straw and pig manure,the key technologies of synergistic and efficient degradation of agricultural wastes with biological pretreatment were explored.By investigating the main factors?carbon to nitrogen ratio,biological pretreatment time,organic loading rate?which affect the anaerobic digestion process,the methane yield and key parameters of anaerobic digestion of agricultural wastes with biological pretreatment were compared and analyzed,and the hydrolysis and anaerobic digestion process of rice straw and pig manure under the condition of biological pretreatment were discussed.In addition,by studying the kinetics of rice straw and pig manure with biological pretreatment,analyzing and comparing the changes of key kinetic parameters,the effects of bio-pretreatment with microbial consortium on anaerobic digestion of rice straw and pig manure were further explored.The main results were as follows:?1?The results of synergistic bio-degradation showed that:When the carbon to nitrogen ratio was 16:1,the highest activities of filter paper cellulase and carboxymethyl cellulose enzyme?CMCase?secreted by microbial consortium could reach 3.2 and 10.8IU/mL respectively,and substrate weight loss ratio was 26.2%;When the initial oxidation-reduction potential was-31 mv,the highest activities of filter paper cellulase and CMCase in degradation solution could reach 2.68 and 4.68 IU/mL respectively,and substrate weight loss ratio was 34.2%;When the feed to water ratio was 11%,the highest activities of filter paper cellulase and CMCase in degradation process could reach 2.58 and6.8 IU/mL respectively,and substrate weight loss ratio was 38.2%.?2?The results of batch anaerobic digestion showed that:When the ratio of carbon to nitrogen was 30:1,the methane yield of rice straw and pig manure after biological pretreatment reached 318.14 mL/g-VS,which was 38%of higher than that without pretreatment.Furthermore,the methane yield?263.69 mL/g-VS?of RS and PM mixtures was obtained through 30 h of biological pretreatment by this cellulolytic microbial consortium,which was 47.6%of higher than that without biological pretreatment.?3?The continuous anaerobic digestion results showed that the anaerobic digestion of rice straw and pig manure after biological pretreatment with the microbial consortium could be performed very stable at organic loading rates ranged from 0.4 to 2.5 kg COD/?m3d?after pretreated by the microbial consortium.The maximum volumetric methane production rate?0.64 L CH4/?L d??and methane yield(0.4557 L CH4/g CODremoved)were62.4%and 37.8%of higher than those without bio-pretreatment.?4?The results of anaerobic digestion kinetic study showed that the first-order kinetic and modified Gompertz models proposed in rice straw and pig manure anaerobic digestion reveal very high fitting properties?R2?0.966?.After pretreatment with microbial consortium,the hydrolytic constant,maximum accumulative methane production and maximum methane production rate of rice straw and pig manure reached 0.46/d,350.79mL/?g-VS?and 45.36 mL/?g-VS d?respectively,which were 77%,45.1%and 84.3%of higher than those without pretreatment.In addition,the lag phase and effective methane production time after bio-pretreatment decreased from 2.43 to 1.79 and 10.7 to 8.92 days,respectively.The above results fully showed that cellulolytic microbial consortium had great potential in improving the hydrolysis efficiency of rice straw and pig manure and the methane yield of their subsequent anaerobic digestion.The purpose of this study was to explore the efficient disposal method of rice straw and pig manure,and to provide technical reference for the conversion of other agricultural wastes resource. |
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