| The organic matter content in food waste is high. It can realize the resource and quantitative reduction of food waste by using anaerobic digestion. There are lots of factors effecting on anaerobic digestion of food waste. It makes it difficult to run stably for anaerobic digestion for a long time.This experiment was done in pilot scale(1.6m3) at different temperature. In this way, we studid the stability of anaerobic digestion of food waste by gradually increasing the organic load rate. At the same time, the ammonia inhibition in anaerobic digestion of food waste, and the treantment of biogas slurry were also studied in this paper.(1) It is demonstrated that under the condition of acid phase at mesophilic temperature-methanogenic phase at thermophilic temperature, the maxmium loading rate of the acidogenic reactor and the methanogenic reactor was 29.27, 6.04 kgVS/(m3·d), respectively. At this condition in acid reactor, the concentration of volatile acids was 5613.6 mg/L. In methanogenic reactor, the biogas production was 0.913 m3/(kgVS·d). The gas production rate of average volumetric was 5.61 m3/(m3·d), and the content of average methane was 73.07%. The total cell density was 2.41×109 cells/ml, while the methanogen density was 7.08×108 cells/ml.(2) While at the condition of acid phase at mesophilic temperature- methanogenic phase at mesophilic temperature, the maxmium loading rate of the acidogenic reactor and the methanogenic reactor was28.1, 5.8 kgVS/(m3·d), respectively. At this condition in acid reactor, the concentration of volatile acids was 9368.2 mg/L. In methanogenic reactor, the biogas production was 0.9 m3/( kgVS·d). The gas production rate of average volumetric was 5.19 m3/(m3·d), and the concentration of average methane was 75%. The total cell density was 4.22×109 cells/ml, while the methanogen density was 4.16×108 cells/ml. Using high throughput sequencing method, it can be found that, as to genus level of the archaea flora, Methanospirillum was the main dominant bacteria in the whole experimental period. As to phylum level of the microbial flora, Firmicutes and Bacteroidetes were the two major dominant bacteria in the whole experiment.(3) In this experiment, a bench scale two-phase(the volume of the acidogenic reactor and the methanogenic reactor was 4.5 L, 5 L, respectively) anaerobic digestion at thermophilic temperature was used to study variations of ammonia concentration in the methanogenic reactor. The results shows that, when OLR was 7.3 gVS/(L·d), the ammonia concentration was 5386 mg/L. Continue to increase OLR to 7.7 gVS/(L·d), ammonia concentration reached 6144 mg/L. Daily gas production began to decline. By adding water and stopping feeding when ammonia inhibition occurred in the system, the ammonia concentration decreased to 3822 mg/L. Then fed again. When OLR was 3.4 gVS/(L·d), the concentration of ammonia nitrogen increased to 4586 mg/L. By using high throughput sequencing method, it can be found that Methanoculleus can tolerate high concentration of ammonia nitrogen in genus level of archaea flora, which was the dominant bacteria in the system at high ammonia condition. At phylum level of microbial bacteria, Firmicutes was the dominant bacterial, followed by Bacteroidetes.(4) Effect of different steam explosion pretreatment on anaerobic digestion of food waste slurry floc was studied in this experiment.The results show that under the condition of maximum pressure 3.0 Mpa, the concentration of ammonia and COD were the highest level(2933.35 and 306575.0 mg/L, respectively). The daily gas production peak was earlier, and the cumulative gas production reached the maximum, 1281 ml. |
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