Study On Methanogenicenhancement Methods Andmicrobial Mechanisms Of Ruralmultiple Organic Waste

In recent years,the rapid development of the rural economy and rural living conditions have gradually improved.As a result of the rapid development of rural production and life,the production of organic waste has also increased gradually.To respond to the development strategy of rural revitalization and build beautiful countryside,the resourceful and clean utilization of rural organic waste has become an inevitable choice.Among the many rural organic wastes,cattle manure and food waste are often treated by anaerobic digestion,and the treatment of vegetable waste is currently mainly based on fermentation for fertiliser production.However,there are many types of organic waste generated in rural areas,and it is a big challenge to realize the unified treatment and resource utilization of multiple organic wastes.As a result of the nature of the substrate and C/N imbalance,previous studies of anaerobic digestion of single substrates such as cattle manure and food waste have often found that the system produces low methane production and allows easy acidification.To solve these problems,this thesis proposes a multi-substrate synergistic anaerobic digestion approach based on several common rural organic wastes that balances the nutrient composition of substrates while facilitating the centralised treatment of organic waste.To this end,three common rural organic waste substrates,cattle manure,food waste,and vegetable waste,were used for co-gas production research in this thesis,and an exogenous conductive medium,activated carbon,was introduced to investigate its effect on the co-digestion and gas production performance of the mixed substrates.To better investigate the microbial influence mechanism of activated carbon on the co-digestion of mixed substrates,the microbial community structure was investigated utilizing microbial high-throughput sequencing technology.The main findings were as follows.(1)The effects of different feeding ratios of mixed substrates on the gas production performance of anaerobic digestion showed that when the mixing ratio of cattle manure,food waste and vegetable waste was 2:2:1(based on VS),the cumulative methane production of the system was the highest(514 m L/g VS),and the methane production was increased by up to 83% compared with that of the single substrate(cattle manure)digestion group;there was a good synergistic anaerobic effect between different substrates with a synergistic index of 1.65;the three substrate co-digestion shortened the delay period of reaction and contributed to the shortening of anaerobic digestion cycle;co-digestion solved the problem of easy acidification of food waste and avoided the accumulation of a large amount of volatile fatty acids in the system,and the alkalinity in cattle manure and ammonia generated from the hydrolysis of nitrogenous organic matter in vegetable waste could effectively neutralize the acidic environment and reduce the risk of acidification.(2)The study on the effect of two activated carbon materials(granular activated carbon and powder activated carbon)in enhancing anaerobic gas production showed that both granular activated carbon and powder activated carbon could effectively increase the cumulative methane production of the system and shorten the delay period of anaerobic digestion;the experimental group with 4 g of powder activated carbon added had the highest methane production,which increased the methane production relative to the control group by 18.67%.The addition of activated carbon promoted the conversion of butyric acid and valeric acid to acetic acid,effectively avoided the accumulation of butyric acid and valeric acid,and accelerated the process of anaerobic digestion.(3)The effects of activated carbon on the microbial community in the anaerobic digestion system showed that different types of activated carbon materials and different additions had different effects on the microbial community in the digestion system: one effect was to increase the dominance of certain microorganisms and form a dedicated and efficient gas production pathway in the digestion system;another effect was to make the microbial community and gas production pathway more diverse;in addition,the addition of granular activated carbon In addition,the addition of granular activated carbon enriched the methanogenic microorganisms related to the acetic acid type,and the addition of powdered activated carbon enhanced hydrogen trophic methanogenic pathway,thus increasing methane production;the functional prediction of microbial communities based on the FAPROTAX database further confirmed the two types of enhancement.