| The generation amount of food waste has been increasing with the development of society and economy, and the demand of safe and efficient disposal of food waste has become an urgent issue. Anaerobic digestion is becoming one of the optimal choices for food waste disposing due to the clean energy generation such as hydrogen and methane. Two-phase anaerobic digestion technique can not only improve the treatment efficiency of food waste, but also obtain both hydrogen and methane. Therefore it has become a research hot spot.In this paper, the changes of biogas yield, the concentrations of organic acids, carbohydrate, protein and related enzyme activities during two-phase and single-phase anaerobic digestion processes of food waste were analyzed, to achieve the optimal operation conditions of two-phase anaerobic digestion. On this basis, the efficiency of hydrogenogenic phase was regulated by adding extrinsic sodium oxamate to inhibit lactic acid generation; the performance of methanogenic phase was improved by acclimating the sludge to sodium acetate and enhancing the endurance of sludge to acetate. Via the regulation technology of two phases, the processing efficiency of food waste by two-phase technique was enhanced, which can be provided as a theory basis to the efficient operation of food waste two-phase processing technique.The main results are as follows:The highest hydrogen and methane production rates of two-phase anaerobic digestion of food waste reached 14.12 m L/g TS and 178.3 m L/g COD, respectively, and both hydrogen and methane production rates increased with the rising of initial p H in the hydrogenogenic phase. The methane production rate in two-phase anaerobic digestion was higher than that of single-phase anaerobic digestion by 338%; meanwhile, the two-phase anaerobic digestion could also obtain hydrogen. The activities of all kinds of enzymes showed a trend of first increasing then decreasing trend in both two-phase and single-phase anaerobic digestion system; the highest activities of amylase, protease and dehydrogenase during two-phase anaerobic digestion were 0.542 mg/(m L·min), 1.70 μg/(m L·min) and 145 μg/(m L·h) respectively, all of which were higher than those during single-phase anaerobic digestion.The food waste hydrogenogenic phase experiment groups were set up with different adding concentrations of sodium oxamate, the concentrations of which were 0, 0.8, 1.2, 1.6 and 2 g/L, respectively. The results showed that with 1.6 g/L sodium oxamate addition, the hydrogen yield and degradation rate of food waste during natural acidification achieved the highest level. The accumulative hydrogen yield and hydrogen production rate was 1183 m L and 18.84 m L/g TS respectively, which were 1.82 times of those in the control group; the TS and VS degradation rates of food waste reached 64.09% and 65.32%, which were 1.20 and 1.16 times of those in the control group, respectively. The generation of lactic acid could be inhibited when a certain concentration of sodium oxamate was added, and then the hydrogen production could be increased.The acclimation of methanogenic sludge with the increasing concentration of sodium acetate step by step was indicated in order to improve the acid tolerance activity of the sludge. The different acetate concentrations of 0, 2, 3, 4, 5 and 6 g/L were set up. The methane yield and dehydrogenase activity were rising gradually during the acclimation process. The acclimated methanogenic sludge was inoculated to the methanogenic phase to treat the effluent from hydrogenogenic phase. The results indicated that the sludge acclimated by 5 g/L acetate had the best performance for degradation of the effluent from hydrogenogenic phase, and the methane production rate, degradation rates of COD and carbohydrate, dehydrogenase activity achieved the highest level, with the value of 173.4 m L/g COD, 40.5%, 53.6%, 183.0 μg/(m L·h), which were 1.41, 1.16, 1.18, 1.26 times of those in the control group, respectively. |
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