The Research On Anaerobic Co-digestion Of Food Waste And Landfill Leachate

Based on the reality of many food waste disposal facilities were built nearby municipal solid waste landfills,this thesis put forward the idea of combined anaerobic digestion of food waste and leachate.The idea is that the microbial community and humus in the leachate could form a transmembrane potential,which have an important effect on the anaerobic digestion of the kitchen waste,thus improving the anaerobic digestion efficiency.In this paper,combined anaerobic digestion experiments carried by single phase sequencing batch were studied,which the food waste,fruit and vegetable waste and kitchen waste were introduced as digestion raw materials,and the leachate,biogas slurry and water as digestion solution respectively.The experimental results show that the synergistic effect of leachate and food waste anaerobic digestion system was mainly in three aspects.Firstly,it accelerates the launch rate of digestion reaction system,which the leachate accelerates the digestive response start of food waste by 5 days,the fruit and vegetable waste increased by 2 days,the kitchen residue increased by 10 days,respectively;the second is to improve the system biogas production rate and biogas yield,as a matter of fact,the addition of leachate increased the peak gas production rate by more than 2 times,and the gas production was improved to varying degrees;thirdly,the combined anaerobic digestion can improve the leachate's biodegradability index(BOD/COD),after combined with the food waste to anaerobic digestion,the BOD/COD of the landfill leachate increased from 0.0492 to 0.6555~0.7035.By examining the change characteristics of parameters such as biogas production rate,methane concentration,pH and VFAs in the anaerobic digestion process,it found that the optimum initial load rate of combined anaerobic digestion was 40 g TS/L,and the optimum ammonia nitrogen concentration was 2000~2500 mg/L.Under the conditions of initial loading rate of 40 g TS / L and ammonia concentration of 2000 mg / L,the gas yield of unit dry food waste was 1452 m L/g TS,the peak biogas production accounted for 74.11% of the total amount of biogas.The methane concentration reached 66% on the second day after the start of the experiment,and then fluctuated within the range of 55% ~76%.While in the system which the initial loading rate was 40 g TS/L and the ammonia nitrogen concentration was 2500 mg/L,the gas yield of unit dry material reached 1308 m L/g TS,and the peak biogas production accounting for 68.51% of the total amount of biogas,the methane concentration remained at around 60%.Fluorescence region analysis(FRI)was applied to quantitatively analyze the composition characteristics of dissolved organic matter(DOM)in biogas slurry.Compared all intensity of fluorescence(?T,n)of each group of biogas slurry,and found that,under the condition of the initial load ?30g TS / L,ammonia concentration ?2000mg/L,the biogas slurry ?T,n value is greater than or close to the ?T,n value of the leachate.This phenomenon is indicating that the easily degradable organic matter in biogas slurry was fully degraded,non-fluorescent substances significantly reduced,and the fulvic acid was the main organic compound in the DOM.Based on four-stage anaerobic digestion theory and related researches of domestic and foreign,and combined with the basic characteristics of food waste and leachate analysis and results of the combined anaerobic digestion experimental,this thesis systematically analyzed the effect of microbial community and DOM in the leachate on the anaerobic digestion of food waste,and expounded the synergistic enhancement mechanism of combined anaerobic digestion between food waste and leachate.There are a large number of micro-organisms which from the landfill in leachate,and dominate the micro-organisms are varieties of hydrolyzed fermentation bacteria and methanogens.After mixing the leachate and food waste,the living environment of the microbial community has been greatly improved,and the hydrogen-producing acetogens began rapid growth and reproduction.Meanwhile,the same type of acetic acid bacteria and hydrogennutrient methanobacterium could use molecular hydrogen,which can reduce the hydrogen partial pressure in the system and providing essential thermodynamic conditions for producing hydrogen-producing acetogens,further accelerated the process of acetic acid.Thus forming and strengthening a gas production peak in the anaerobic digestion system.Then the methanogens began to multiply,and the anaerobic digestion system enters into the methane production stage quickly.