Pilot-scale Study On Anaerobic Digesting Molasses To Produce Biogas, Isolation Of Associated Microorganisms And Bioaugmentation Test

Sugar cane molasses is one of the by-products produced in the sugar making process of sugar factories.It has the characteristics of high COD content,complex composition,rich colloidal impurities and large dry matter concentration.The content of fermentable sugar contained in molasses can reach 30%to 50%,which is a good fermentation raw material.In the context of the global energy crisis today,biogas,as a renewable energy source that can be obtained through anaerobic fermentation,has great potential for development.Due to the large amount of molasses production and the small amount of demand in Guangxi Province,it is possible to use molasses for anaerobic fermentation to produce biogas.However,there are few reports on related aspects.Based on the laboratory-scale small-scale experiment,the experiment used sugarcane molasses as a substrate,and used the IC anaerobic reactor with external circulation pump to carry out pilot anaerobic fermentation to explore the feasibility of producing biogas by anaerobic fermentation of molassesThis experiment is divided into early stage pilot test fermentation and fermentation in flasks for bio-enhancement experiments.The early stage pilot test fermentation was carried out by an anaerobic treatment of diluted molasses using an IC reactor with a volume of 2.3 m~3.The reactor was fermented at a natural temperature(20 to 3 8?),and an external cycle was added after the start-up period to enhance the efficiency of the fermentation.Without adding any nutrients and buffers,the daily influent water is 400 L,the hydraulic retention time is 5 d,the highest influent load is 2500 mg/L,the highest COD removal rate is 88.00%,and the highest daily biogas output is 2.4 m~3,the gas production rate reached 0.58 m~3/kg,and the methane content in the biogas reached 49.8%.In the later stage,the microorganisms in the activated sludge obtained in each stage of the pilot fermentation experiment were enriched,screened,isolated and identified.The sludge samples obtained in the previous experiments were divided into A1-A4,B1-B5 according to the period(A:before the instalment of the external circulation;B:after the instalment of the external circulation),and cultured under three temperatures of 25?,30?,and 37?.Colonies with different growth conditions at three temperatures were isolated.Each obtained colonies was treated with colony PCR and sent for the 16S rDNA sequencing,the obtained sequences were compared in the NCBI website with BLAST.It was found that the main bacterial microflora in the A-stage sludge was Leuconostoc and Acinetobacter and Bacillus,and the B-stage was Lysinibacillus and Leuconostoc.The genus Leuconostoc could be screened throughout the anaerobic fermentation process.The 17 strains obtained from the experiments could grow in the medium with molasses as the sole carbon source.The A3 sample microflora with the best growth condition during the culture was used for the bio-enhancement experiment in the fermentation flask.The fermentation flask experiment also uses the diluted molasses as the fermentation substrate for the anaerobic fermentation.After the acclimation period is completed,the A3 sample microflora is added for the bio-enhancement,and a total of 3 different bacterial liquid volumes of 1%,3%,5%and a control were used.The experiment found that the experimental set with 3%bacterial liquid volume had the best treatment effect,the COD removal rate reached 88.63%,and the ammonia nitrogen removal amount and the decrease amount of VFA were higher compared with the control set and the other two sets.The results of the study indicate that the experiment of molasses at the pilot level is feasible and has the potential of industrialization;the most isolated strain from the sludge sample obtained from the pilot fermentation is Leuconostoc directly in the 250 mL fermentation flask The bio-enhancement method of adding mixed bacteria has a certain promoting effect on the anaerobic fermentation of molasses,which lays a theoretical foundation for the production of biogas by large-scale fermentation of molasses.