| Two Stage Anaerobic Digestion(TSAD)is a bioenergy technology that separates the hydrogen production stage and the methane production stage.It can improve the conversion rate of organic waste by controlling the reaction conditions of the two stages.However,the current two-stage anaerobic digestion process has problems such as poor system stability and low gas production efficiency.Therefore,in order to strengthen the performance of two-stage anaerobic digestion,this paper takes food waste as the research object,and explores the effects of different red mud addition amount,hydrothermal pretreatment temperature and biogas slurry recirculation ratio on the two-stage anaerobic digestion process of food waste,so as to provide reference for engineering application.The main research contents and experimental results are as follows :(1)The effect of red mud addition on the performance of two-stage anaerobic digestion was studied.Firstly,the effect of red mud addition on the hydrogen production performance in the first stage of dark fermentation was investigated.When the red mud addition was changed to 11 g/L,22 g/L,33 g/L and 44 g L,the cumulative hydrogen production was 126.36 m L,135.15 m L,132.4 m L and 127.5 m L,respectively,which was 27.1%,35.6%,33.2% and 28.3% higher than that of the blank group.The addition of red mud promoted the fermentation of butyric acid and acetic acid,improved the hydrogen production pathway,and thus increased the hydrogen production.The modified Gompertz model was used for analysis,and the results showed that the lag phase of hydrogen production was shortened from 10.2 h to 6.7 h.The experimental results showed that the addition of red mud promoted the hydrogen production performance in the first stage of dark fermentation.Secondly,the effect of red mud on the performance of methane production in the second stage of anaerobic digestion was investigated.The results showed that when the addition amount of red mud was 33 g/L,the cumulative methane production was 660.2 m L,which was 75.6%higher than that of the blank group.The modified Gompertz model was used for analysis.The results showed that the lag period of methanogenic stage was shortened from 6.57 d to 4.44 d,and the ETS activity of 33g/L red mud addition group was 24633μg/(m L h),which was 66.4%higher than that of the blank group.The concentration of coenzyme F420 was 0.0754μmol/g,which was 75%higher than that of the blank group.The conductivity was 1687μs/cm,which was 81.2%higher than that of the blank group.The experimental results show that the addition of red mud promotes the second stage methane production performance.The performance of two-stage anaerobic digestion was investigated.When the amount of red mud was 33 g/L,the total energy output was 10.06 k J/g-VS,which was128% higher than that of the blank group.The removal rates of TS,VS and COD were 38.7%,69.2% and 67.2%,respectively,which were 36.7%,20.1% and 15.7%higher than those of the blank group.It shows that adding red mud can improve the performance of two-stage anaerobic digestion.(2)The effect of hydrothermal pretreatment temperature on the performance of two-stage anaerobic digestion was studied.The hydrothermal pretreatment temperatures of the experimental group were 50 °C,80 °C,110 °C,140 °C and170 °C,respectively.The results showed that when the hydrothermal pretreatment temperature was 140 °C,the soluble polysaccharide content in food waste was13929.44 mg/L,which was 3.29 times that of the blank group.The cumulative hydrogen production was 138.875 m L,which was 39.7% higher than that of the blank group.The cumulative methane production was 892.7 m L,which was 1.9 times higher than that of the blank group(299.9 m L).It shows that when the hydrothermal pretreatment temperature is 140 °C,it can better promote the two-stage anaerobic digestion performance.The effect of hydrothermal pretreatment combined with red mud on the performance of two-stage anaerobic digestion was studied.The experimental groups were 140 °C hydrothermal pretreatment combined with 33 g/L red mud addition group,33 g/L red mud addition group and hydrothermal pretreatment group.The results showed that the hydrogen production of the group with 33 g/L red mud after140 °C hydrothermal pretreatment was 141.58 m L,which was 42.4% higher than that of the blank group.The methane production was 921 m L,which was 207 % higher than that of the blank group.The total energy output value was 12.802 k J/g-VS,which was 1.9 times higher than that of the blank group.It shows that 140 °C hydrothermal pretreatment combined with 33 g/L red mud can better promote the formation of hydrogen and methane.(3)On the basis of hydrothermal pretreatment and red mud addition in the twostage anaerobic digestion process,a 2 L-5 L two-stage reactor was used to explore the effects of biogas slurry recirculation ratios of 0.1,0.2 and 0.3 on the two-stage anaerobic digestion performance.The results showed that when the biogas slurry recirculation ratio was 0.1,the hydrogen production rate was 352.4 m L/d,which was4.4%-28.1% higher than that of other groups.The hydrogen content was 50.2 ±1.9%,which was 4.1%-16.5% higher than that of other groups.The average rate of methane was 268.29 m L/d,which was 15.1% higher than that of the blank group.In the two-stage anaerobic digestion process,it was found that when the biogas slurry recirculation ratio was 0.1,the removal rates of TS,VS and COD were higher,which were 51.4%,87.1% and 73.6%,respectively.It shows that when the biogas slurry recirculation ratio is 0.1,the two-stage anaerobic digestion performance and organic matter removal rate can be better improved. |
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