Anaerobic Treatment Of Molasses Vinasse With Different Manure As Mixed Raw Materials: Analysis Of Differences In Efficiency And Microbial Structure

Molasses,a by-product of sugar production from sugarcane,which is widely used in alcohol production.However,in the process of alcohol production,high concentration molasses vinasse will be produced.For this kind of difficult-to-treat medium-high-strength organic wastewater,anaerobic digestion is undoubtedly one of the most suitable treatments for reducing wastewater pollution.However,molasses vinasse has chemical characteristics of low pH value,high soluble chemical oxygen demand（SCOD）and high sulfate content of molasses vinasse,stable operation of the anaerobic digestion system is difficult when using molasses vinasse as the only feedstock.Anaerobic co-digestion can utilize the balance between substrates to better dilute toxic substances.It has the advantages of enhancing energy recovery,and tolerating high organic loading rate（OLR）.It can make up for the adverse effects of raw material properties on single digestion.Studies have shown that animal manures have a promoting effect in improving anaerobic co-digestion.The effect of anaerobic digestion depends on the type of mixed substrate,the ratio of mixed substrate and substrate concentration.In addition,the selection of inoculated sludge is also important.In this paper,the anaerobic co-digestion of different animal manures and molasses vinasse is proposed to analyze the anaerobic digestion effect and the dynamic changes of microbial structure,so as to provide a reference for the efficient anaerobic treatment of molasses vinasse.In this study,swine manure,chicken manure and cattle manure were selected as co-digestion substrates of molasses vinasse（SM group,CM group and BM group respectively）,and the anaerobic digestion effects of the three groups were compared under different conditions in different stages.Anaerobic digestion can be divided into stage Ⅰ and stage Ⅱ.Stage Ⅰ is the 4th-32nd day of co-digestion.In this stage,the OLR is the same,but the proportion of animal manures SCOD:molasses vinasse SCOD is different（according to 1:1,1:3,1:5,1:7 and 1:9respectively,animal manures SCOD gradually decreases and molasses vinasse SCOD gradually increases）.Stage Ⅱ is the 32nd-104th day of the anaerobic digestion effect.On the basis of stage Ⅰ,select the best proportion and keep the proportion（1:7）unchanged to continuously improve the influent OLR.The results showed that in stage Ⅰ,the reactors in each group showed better digestion effect at the ratio of 1:7,and the CM group was relatively better.As the ratio increased to 1:9,the anaerobic digestion performances of all groups obviously decreased,while the BM group was more stable,with its SCOD removal rate 11.7%and 12.2%higher than for the SM and CM groups,respectively.In stage Ⅱ,the SCOD removal efficiency of the CM group was the best and reached 70.9±0.4%.The microbial community analyses indicated that the hydrogenotrophic methanogen Methanobacteriaceae were dominant in the CM group.In addition,Synergistaceae with the function of acetogenesis,and Anaerolineaceae with the function of hydrolyzing polysaccharides,were enriched in stages Ⅰ and Ⅱ,respectively.In stage Ⅰ with the ratio of 1:9,the Anaerolineaceae and acetotrophic methanogens Methanosarcinaceae played an important role in the BM group.The research results provide a reference for the treatment of animal manure as a substrate for anaerobic co-digestion of molasses vinasse.In order to analyze the stress resistance of activated sludge in different animal manure mixed digestion tanks,the activated sludge produced by anaerobic co-digestion of swine manure,chicken manure and cattle manure were used as inoculation sludge（SMS,CMS and BMS respectively）.Under the impact of molasses vinasse with high OLR and high concentration of sulfate,the anaerobic digestion effect of the three kinds of mixed sludge was compared.The results showed that when the OLR of molasses vinasse was 6.0 g_SCOD·L^-1·d^-1,the SCOD removal rate of each group was the highest,and the CMS group was 3.5%and2.9%higher than the SMS group and BMS group,respectively.Under the impact of high sulfate concentration,the digestive performance of each group showed a downward trend,and the CMS group was less affected.Based on the anaerobic performance of the reactor in each stage,the sludge domesticated with chicken manure has better digestion effect under the impact conditions of high OLR and high concentration sulfate of molasses vinasse.The microbial community structure under impact conditions showed that the dominant population types of each group were almost unchanged,and the change of specific flora abundance may be the reason for the difference of sludge stress resistance.