| Because of its rich organic matter content,high water content,and a wide variety of microorganisms,the hogwash waste grease is both a pollutant and a resource,and waste oils can not be effectively removed with traditional treatment methods in daily life.Anaerobic fermentation can convert waste into its own carbon source,synthetic PHAs and raw materials for clean energy such as methane and H2 ——Volatile Fatty Acids(VFAs).A large number of studies have shown that protein and carbohydrate types of kitchen waste are mainly producing even carbon VFAs,and there are few reports on the production of odd carbon VFAs from waste grease,which are used to improve the denitrification and dephosphorization of wastewater.Studying the anaerobic fermentation of waste to produce acid can simultaneously realize the recycling of hogwash waste grease and continuous production of green energy,which has broad development prospects.This project aims to optimize the process of producing odd carbon VFAs from hogwash waste grease and analyze the internal composition.The experiments were mainly used lame waste oil as the research object,and divided into three categories.The batch test was used to study the variation law and characteristics of the odd-numbered carbon VFAs produced by the hogwash waste grease types withoutcontrolling the influence factor,and selected one of the fermenting substrates that can be produced by odd carbon VFAs and the highest proportion.Firstly,the effects of different conditions on the production of odd carbon VFAs and their mechanisms were investigated by comparing the actual and simulated conditions.Secondly,several external influences(inoculation sludge,ratio,p H value,ORP value,glycerin addition)were used to optimize the acid production of the waste on this basis,and the optimal conditions for promoting the production of odd carbon VFAs by a single oil were determined.Finally,based on 16 s RNA high-throughput sequencing technology to detect its internal structure,determine the dominant genus that affects the production of odd carbon VFAs.The outcomes showed that among three types of hogwash waste grease,the fat was the waste that can produce more odd carbon VFAs and was easy to obtain,and the dissolved protein and acidification rate were higher.When the influence factor was not controlled,the odd carbon VFAs reached up to 3356.47 mg/L,accounting for 60.47% of the total VFAs content.Compared with the fat and pure fat meat,the content of odd carbon VFAs and the proportion of the change in the fermentation process were similar.In the influencing factor test,the best ratio of fat and sludge was VS sludge: VS fat = 2:1,the best p H range was 6~7,the best ORP range was 100~200m V,the best investment of glycerol was C:N=30:1 when the amount of fat-glycerin co-fermentation,the odd-numbered carbon VFAs reached up to7905.08mg/L,accounting for 91.86% of the total amount of VFAs,which were much higher than the single matrix fermentation without the influence factor.In the analysis of microbial community,in the analysis of genus level,the relatives of Veillonella,Acinetobacter and Pseudomonas were abundance dominated in fat and fat-sludge,and the V.parvula,which promoted propionic acid,promoted the production of propionic acid.Among the glycerol samples,Pseudomonas mainly promoted the production of odd-numbered carbon VFAs.The dominant bacteria in the fat-sludge-based bacterium belonged to the dominant genus,which increased the intrinsic conversion rate and increased the odd-numbered carbon VFAs.Therefore,fat in the hogwash waste grease was significant in the production of oddcarbon VFAs.The fat meat can be hydrolyzed and acidified to produce a large amount of glycerol and converted into propionic acid,which solved the problem that all types of waste anaerobic fermentation produced acid types of even carbon VFAs. |
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