| As a kind of Biomass substrate,the municipal solid wastes,can be made into biogas by AD(Anaerobic digestion),and the recidue can be used to produce organic fertilizer if composted.However,as a kind of complex organic matter,the AD process adopted should be stable and adaptive to the complex substrate.Besides,to take environmental and economic factors into consideration,to reduce the water consumption and the cost of recidue process is also necessary when dealing with such substrate.In this study,the organic matter of municipal solid waste is used as the substrate.A dry-AD-state acid phase is established in a filter bed reactor,while a liquid methane phase is established in a biofilm fixed bed reactor.By studying the hydrolysis-acidification process in the acid phase,the cultivation of the biofilm and the biogas yield characteristics of the solid-liquid two-phase AD,the following conclusions can be reached:(1)By studying the hydrolysis-acidification process with different inoculation ration in the filter-bed reactor,the following conclusions are obtained: Hydrolysis-acidification process is dominant during the early reaction,along with the consumption of the RDO(Readily degraded organic)in the substrate,the process transforms from acidification to methanation,However,by analysing the cellulose in the substrate,there is still plenty of organic matter that is not hydrolyzed in the substrate.The relative rise of substrate inside the reactor leads to the increase of soluble organic matter in the acid liquid,but the level of hydrolysis-acidification process does not increase relatively.Most of the organic matter in the acid liquid still exists as dissolved organic matter.(2)To cultivate the biofilm of the biofilm fixed bed actor,the glucose and the acid liquid produced by the acid phase is used as feed,and the HRT(Hydraulic retention time)of the biofilm fixed-bed reactor is reduced to increase its organic loading.Meanwhile,the study of microbial proliferation was supported by polyurethane packing anaerobic digestion in fermentation bottles.The biofilm can be cultivated steadily by two-stage cultivation with glucose and acid liquid,without undulated failure of the reactor.During the acid cultivation,the early marsh liquid has a relatively strong ability of hydrolytic acidification,but hydrolytic acidification becomes weaker while Methanogens enriched.When the filler works as a carrier of microorganisms,the growth cycle of microorganisms extends.But after the cultivation,the activity of Methanogens is improved at the same time.(3)Based on the research of the first two parts,a integrated solid-liquid two-phase AD system is established,and the result is compared with the methane yield experiment of the substrate.In the 15 days of acid production,though the practical gas yield is only 20% of the methane yield experiment,the methane yield can be about 40% of the theoretical value.After the hydrolytic acidification phase,there is still lots of organic matter left in the solid substrate,which needs to be degraded sostenuto by the microorganisms.According to the data of the biofilm cultivation of the methane phase,there is still room that HRT can be reduced.(4)Based on the research of the microbial communnity structure by the residue from the acid phase,the biofilm and slurry from the methane phase,The biofilm contains a lot of bacteria which can be involved in hydrolysis-acidification process reaction.And the microbial diversity of residue was in a low level,But the bacteria of hydrolysis-acidification has been enriched.Clostridiales,Bacteroidales,Synergistales,accounted for about 35~45% of the total bacteria,were advantage bacterium group.In the slurry,the Chromatiales has a high relative abundance while with a poor adhesive property for the polyurethane packing.In the aspect of archeaes,the methanosaeta and the methanosarcina has high relative abundance by the packing provides a gathering place.Meanwhile,With a poor adhesive property,the Methanospirillum has a low relative abundance in the biofilm. |
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