| A huge amount of kitchen waste was produced in China,with a solids content of about 25% and a high organic matter content.Traditional landfill treatment of kitchen waste may produce more leachate and occupy a larger area,so that kitchen waste is urgently looking for other treatment methods.Anaerobic digestion technology can not only achieve reduction and harmlessness of kitchen waste,but also recycle biogas,which would be an important development direction for the treatment of high-solid kitchen waste in the future.Traditional wet anaerobic digestion technology was mostly used for waste water,sludge,manure and other wastes with low-solid content,however,the composition of kitchen waste with high-solid content was complex,so it was difficult to adopt wet digestion technology.Therefore,this paper conducted anaerobic digestion research on single components of kitchen waste,and adjusted the proportion of kitchen waste in the start-up based on the results.It built a new vertical-flow anaerobic digestion system,started in stages,and examined the operation efficiency of the system during the start-up and optimized the temperature and mixing schemes through batch experiments.It analyzed the microbial community structure at each startup stage and compared the differences in microbial community under different temperatures and mixing schemes.The single component anaerobic digestion study on four representative components showed that staple foods,fruits and vegetables were prone to acidification,especially staple foods,the p H quickly drops to about 3.53.And due to the rich cellulose contained in fruits and vegetables,the rate of hydrolysis and acidification was slow.The protein content of meat was high,and the ammonia nitrogen produced by digestion can alleviate acidification,but FAN reached 225.28 mg/L in the late digestion period,and INH3 reached 0.29,resulting in severe ammonia inhibition.Therefore,in the proportion of kitchen waste in the start-up,the proportion of meat could be appropriately increased.Research on the operation efficiency of the vertical-flow anaerobic digestion system for processing high-solids kitchen waste under mesophilic condition(37 ± 1)? showed that after successfully started in three stages the volume loading rate was 9.79 g VS/(L·d),the p H was around 7.50,the total alkalinity was maintained near 4500 mg/L,volatile fatty acids were mainly acetic acid and propionic acid,the VS reduction could reach(80.57 ± 4.10)%,SBP and SMP were(0.878 ± 0.061)L/(g VSadd·d)and(0.476 ± 0.045)L/(g VSadd·d),the system had a enough buffer capacity and a good biogas production ability,and there was no inhibition of acid or ammonia(INH3 were 0.77).After the two important parameters of temperature and stirring scheme were optimized,by comprehensively considering the two factors of system stability and gas production capacity,medium temperature and once daily mechanical stirring were selected.Researches on the microbial community structure at different stages and under different operating conditions showed that during the start-up from a single substrate to a complex substrate,the number of bacteria participating in the hydrolytic acidification phase increased and tended to be average,while archaea responsible for methanogenesis tended to be more specific.After start-up,Chloroflexi(10.11%),Firmicutes(20.94%)and Bacteroidetes(14.68%)accounted for a large proportion,and the dominant genus of archaea was Methanothrix(50.57%).In the parameter optimization process,through cluster analysis and PCA,temperature had a greater influence on the distribution of microbial communities,but Methanothrix and Firmicutes always occupied a large proportion under different operating conditions.This study provided a feasible starting plan reference for the practical project of high-solids kitchen waste disposal,and revealed the regulation mechanism of operating parameters from the microbiological level. |
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