Optimization Of Techonlogical Conditions For Acidogenic Phase By Garage-Type Dry Fermentation

With the continuous advancement of the new urbanization process,China has paid more and more attention to the construction of ecological environment in urban areas.Agriculture,forestry,animal husbandry,etc.as the primary industry are still the basic industry of national life.Therefore,in addition to a large amount of municipal solid waste,China's urban solid waste also contains a large amount of agricultural waste.Food waste is an important part of organic fraction of municipal solid waste,and has a high moisture content.It's perishable and will produce a large amount of leachate.If the food waste couldn't be treated promptly and effectively,it will cause secondary pollution to the water and soil.Agricultural waste mainly consists of crop stalks,which has a low moisture content and high calorific value,and could be biodegraded.The current treatment methods of agricultural waste are mainly based on incineration power generation and anaerobic fermentation to produce biogas.Against this situation,how to deal with the waste in urban areas harmless,reducing,and recycling is one of the most serious problems in the new urbanization construction.The anaerobic fermentation is a relatively mature process for the treatment of solid organic waste at home and abroad.It has a large capacity of disposal,low cost and no secondary pollution.And it can produce a large amount of clean energy,and has made great progress in the past dozens of years.This project used food waste and crop straw as fermentation raw materials,by garage-type anaerobic dry fermentation technology,and used leachate reflux process to optimize its acid phase production.The following conclusions are obtained:(1)Exploring the effect of the type of leachate on the acid production of the acidogenic phase of garage-type dry fermentation.The waste activated sludge(WAS),pig manure(PM)anaerobic fermentation broth and tap water(TW)were selected as the initial spray.The experiment results showed that when used the pig manure anaerobic fermentation broth as the initial spray,the concentration of volatile fatty acids(VFAs)in the leachate peaked at 18.9 g/L on the 4th day,with the acetate content always maintained above 40%,and the peak period can reach 66.43%.The acid production effect is better than the other two groups.(2)Exploring the effect of the reflux ratio of leachate recirculation on the acid production of the acidogenic phase of garage-type dry fermentation.The experiment results showed that when the reflux ratio was 32:1,the acid production was the highest.The pH of the leachate was reduced to a minimum of 6.40 on the 3rd day,the concentration of T-VFAs was as high as 45.45 g/L,with an acetic acid concentration of 25.90 g/L and n-butyric acid concentration of 10.60 g/L,which was a typical butyric fermentation.The TS and VS degradation rates were 59.19% and 61.70%,respectively.And the COD removal rate was 42.83%,both higher than the other groups.The test results showed that the greater the reflux ratio of leachate,the faster the hydrolysis acidification stage proceeds,and the faster the product can be used by anaerobic microorganisms,which can effectively shorten the acid production fermentation time and increase acid production efficiency.(3)Exploring the effect of the frequency of leachate recirculation on the acid production of acidogenic phase of garage-type dry fermentation.The test results showed that when the reflux frequency of leachates was 8 times/d,the acid production was the highest.The pH reduced to a minimum value of 5.73 on the 7th day,and then recovered to 6.36 quickly,demonstrating that the leachate had a strong buffering capacity.The amount of COD elution peaked at 13390 mg/Lon the 3rd day.The T-VFAs production reached its peak on the 3rd day and reached the highest on the 5th day with 12.90 g/L,including butyric 7.40 g/L and acetic 3.30 g/L,which was a typical butyric fermentation.The TS and VS degradation rate reached 57.84% and 59.33%,respectively.(4)Leachate and biogas residue from the group of the best effect of acid production were analyzed for microbial community structure.The abundance of archaeal community was during 85~105,and the bacterial community abundance was during 500~1200.Compared with the methanogenic archaea,the bacterial richness and diversity were significantly higher.The Methanosarcina is methane-producing bacteria of acetic acid,and it can be up to 35.84% in the leachate,as the most dominant group.In terms of bacteria,the Firmicutes and Bacteroidetes were the dominant bacteria,accounting for more than 85% of the total amount of bacteria.