| With the continuous increase of the treatment amount and efficiency of sewage plant in China,the prodution yield of residual sludge,as one of the by-products of sewage treatment,is signifinating increasing.The swage-actived sludge contains a large amount of organic matter,pathogenic bacteria,various heavy metals,other toxic and harmful substances,so it must be effectively treated to reduce its harm to the environment.Anaerobic digestion can produce clean energy while effectively degrading organic matter,and is widely used in the sludge treatment of sewage treatment plants at home and abroad.In recent years,the development of thermal hydrolysis technology has broken through the bottleneck of low anaerobic digestion and hydrolysis efficiency of high solids sludge(solid content greater than 10%).At the same time,it can effectively reduce the volume of the treatment unit and realize the high solids sludge.Efficient processing.In the highsolid sludge thermal hydrolysis-anaerobic digestion process,with the full hydrolysis of organic matter,the higher ammonia nitrogen concentration and high p H value in the digestion tank reduce the stability of the digestion system.How to alleviate the ammonia inhibition in the digestion tank becomes The main research issues of anaerobic digestion of high solids sludge.In addition,food waste is easy to acidify when it is treated by anaerobic digestion.When co-digested with high-solid sludge,it has the potential to alleviate the ammonia inhibition of the high-solid anaerobic digestion system,and at the same time,it can relieve its own anaerobic digestion acid accumulation.This experiment takes the high-solid sludge and kitchen waste(solid content about20%)as the research object,and analyzes different thermal hydrolysis conditions(temperature is 165℃,time is 30 min,60min and 90 min respectively)and different proportions(The mass ratio of food waste to the mixed matrix is 0%,20%,40%,60%,80% and 100% respectively)The influence on the thermal hydrolysis effect of the mixed substrate,and explore the optimal thermal hydrolysis pretreatment conditions Under the optimal pretreatment conditions,carry out continuous experiments of co-anaerobic digestion at medium temperature(35±1℃)and high temperature(55±1℃)to analyze the changes in gas production,anaerobic digestion efficiency and microbial community.Explore the effect of thermal hydrolysis pretreatment on the co-digestion of food waste mixed with excess sludge.The main conclusions are as follows:(1)The thermal hydrolysis batch test results of the high-solid sludge mixed with kitchen waste show that the hydrolysis rate of insoluble organic matter in the mixed matrix gradually increases with the extension of the thermal hydrolysis time.After 30 minutes of thermal hydrolysis,the mixed matrix The hydrolysis rate of insoluble organic matter increases the fastest,and further extension of time(60min and 90min)has little effect on the hydrolysis of insoluble organic matter,that is,30 min is the best pretreatment time.The kinetic analysis of the thermal hydrolysis process was further carried out,and the results showed that the rate of thermal hydrolysis of the residual sludge alone was higher than that of the food waste alone.When the proportion of food waste in the mixed matrix was relatively low,the proportion of food waste in the mixed matrix was relatively low.Dosing will reduce the thermal hydrolysis rate of the mixed matrix,and when the proportion of food waste is higher than 40%,the effect on the thermal hydrolysis rate of the mixed matrix is minimal,so the best ratio is 40% of the food waste.condition.Therefore,the optimal pretreatment conditions for the mixed thermal hydrolysis of surplus sludge and food waste are thermal hydrolysis temperature of 165°C and time of30 minutes,and the best proportioning condition is that food waste accounts for 40%.(2)The continuous test results of the co-digestion of food waste mixed with highsolid sludge show that the mixed matrix with a proportion of 40% food waste is subjected to thermal hydrolysis at 165°C for 30 minutes and then subjected to mesophilic and thermophilic anaerobic digestion.The biogas yields of mild high-temperature anaerobic digestion are 239.78 m L/g VS and 310.19 m L/g VS,respectively,and the VS removal rates are 56.2% and 61.5%,respectively.High-temperature anaerobic digestion is more conducive to the methanation of organic matter in the mixed matrix.This may be due to the higher activity of methanogens in high-temperature anaerobic digestion.The free ammonia concentration in the medium-temperature and high-temperature reactors were22.85±2.29 mg/L and 182.49±14.17 mg/L,respectively,and there was no ammonia inhibition.Therefore,the co-digestion of food waste and high-solid sludge can effectively improve the efficiency of anaerobic digestion and alleviate the phenomenon of ammonia inhibition.(3)The results of the microbial community analysis in the co-digestion stage of the mixed high-solid sludge of kitchen waste show that Methanobrevibacter,Methanothrix and Methanomassiliicoccus are the dominant methanogenic microorganisms in the medium temperature reactor,and Methanothermobacter,Methanomassiliicoccus and Methanothrix are the dominant methanogenic microorganisms in the high temperature reactor.Microorganisms,the methanogens in the two reactors are mainly hydrogentrophic. |
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