| With the fast development of China’s economy and the improvement of people’s living standards,food waste is increasing year by year.Food waste has high content of organic matter.If food waste is not treated promptly and effectively,it will produce stench,breed mosquitoes and flies,and pollute the environment.The aerobic composting process can eliminate the environmental pollution caused by kitchen waste and the compost products can also be used as soil organic fertilizer.Aerobic fermentation can realize harmless,resource and reduction of kitchen waste.However,the effect of aerobic composting is not ideal because of the high oil content and high viscosity of kitchen waste.In addition,the C/N of kitchen waste is relatively low,and nitrogen is easily lost in the form of ammonia gas during the fermentation process,causing secondary pollution and reducing the quality of fermented products.In this study,kitchen waste was used as fermentation raw material,and microbial strains with the ability to degrade oil and nitrification were screened.The effect of bacterial agent and ventilation rate on the aerobic fermentation process of kitchen waste was studied first,and then the oil-degrading ability of degreaser was analyzed.Relevent research results can effectively control the nitrogen loss during the aerobic fermentation of kitchen waste,and at the same time improve the conversion effect of refractory substances such as oils and fats.It has certain academic significance and practical value to strengthen the aerobic fermentation process of food waste by biotechnology.The main research contents and results are as follows:(1)Screening of strains for aerobic fermentation of food waste.Using Jiangnan University canteen food waste as raw material,4 strains of oil-degrading bacteria,2 strains of nitrosative bacteria and 4 strains of nitrifying bacteria were isolated and purified through a specific medium.After molecular identification,the degreaser bacteria strains were Klebsiella aerogenes strain,Lysinibacillus macroides strain,Acinetobacter baumannii strain and Bacillus haynesii strain respectively,nitrisifying strains were Bacillus rhizosphere and Bacillus aerobacterium,and nitrifying bacteria strains were Rhizobium pusense strain,Agrobacterium salinitolerans strain,Stenotrophomonas maltophilia strain and Bacillus tropicus strain respectively.Combined with the strains preserved in the laboratory,the formulations of oil removing microbial inoculants(ORMI)and nitrogen-retaining microbial inoculants(NMI)were obtained.(2)Strengthening aerobic fermentation of kitchen waste with compound microbial agent.The bacterial agents ORMI and NMI were respectively inoculated into the kitchen waste compost for aerobic fermentation.It was found that the inoculation of ORMI had a greater impact on the organic acid concentration in the early stage of fermentation.On the third day,the organic acid concentration increased by 24.48%,which was significantly higher than that of the control and the p H was lower.Inoculation with ORMI could promote the convertion of NH4+-N to NO3--N,and the concentration of NO3--N in the fermentation product increased by 70.38%.Due to the highest concentration of organic acids and the strongest nitrification ability in the early stage of composting in the ORMI group,the final cumulative NH3 emission was reduced by 12.27%.Besides,the ORMI inoculant had the strongest ability to degrade oil,reaching 98.09%.at the 21 st day,the GI reached more than 70%,about 14 days earlier than the CK group.(3)Effect of ventilation rate on aerobic fermentation of food waste.With ORMI as the inoculant,0.1,0.2,and 0.3 L /(min · L piles)were set respectively.Compared with the control,the cumulative emission of NH3 decreased by 25.82%,31.88% and 45.09%,respectively.When the ventilation rate was 0.2 L/(min · L piles),the TKN content of the fermentation product was the highest,which was 10.17% higher than that of the control.With the increase of ventilation rate,the total Kjeldahl nitrogen content decreased to 3.73% of the control.Under different ventilation conditions,the oil degradation rates were 85.77%,88.38% and 78.04%,and the seed germination indices of the fermentation products were 106.24%,113.57% and 85.21%,respectively.In general,the composting effect of kitchen waste with ventilation rate of 0.2 L /(min · L piles)is the best,which can control the organic acid concentration in the early stage of composting in an appropriate range,reduce nitrogen loss,promote oil degradation,and improve the quality of composting.(4)Study on the grease removal characteristics of ORMI.The effects of temperature,p H,salt content,oil concentration and inoculation amount on the growth and removal of oil were studied,and the ability of lipase production was further studied,which provided useful reference for the practical application of the agent.The results showed that the compound oil-removing microbial agent had certain oilremoving ability when the temperature was 25~55℃,the p H was 4~9,the salt content was 5~90 g/L,the oil concentration was 1%~5%(v / v),and the inoculation was 1%~9%(v / v),and the degradation rate of oil can reach as high as 84.75%.The results of single strain showed that strain B501 had the highest lipase activity,but strain 009 had the strongest oil removal ability because of its long duration of high lipase activity.In addition,the oil removal effect of compound bacteria is better than that of single strain.The main conclusion of this study is that inoculation with oil removing inoculum(ORMI)can effectively promote the production of organic acids,reduce the production of ammonia gas,and improve the quality of fermentation products.Appropriate ventilation volume(0.2 L/(min·L piles))can control the appropriate organic acid concentration in the early stage of fermentation,regulate the nitrogen loss in the entire fermentation process,and promote the rapid and efficient fermentation process.Oil-removing microbial inoculum(ORMI)can exert oil removal ability in different oily wastewater,and the oil removal rate can reach more than 80%. |
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