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| Particle hydrolysis during the two-phase anaerobic digestion of vegetable waste |
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Abstract During the two-phase anaerobic digestion process of vegetable waste, changes of hydrolytic acidification liquid’s physical-chemical properties were investigated. The relationship among dissolution of total organic carbon (TOC), dissolved organic carbon (DOC) and particulate degradation was discussed. The mechanism of particle hydrolysis acidification was assessed by combining the trend of TOC, DOC, particle size distribution and molecular weight evolution. The experiment results showed that, the hydrolysis process of vegetable waste could be divided into two stages. In the first five days, particulates with high degree of hydrolysis began to hydrolyze quickly. The TOC value rose rapidly, reaching the maximum of 4920mg/L in the fifth day. The quadratic mean diameter of particulates generated from hydrolysis dropped from 58.38 μm in the first day to 4.64 μm in the fifth day. Furthermore, organic matter dissolved rapidly, with a maximum of 85% DOC/TOC ratio. This process could be simulated by Contois hydrolysis model. After the fifth day, the slow hydrolysis of difficult recalcitrantly-hydrolyzed particulate played a dominant role. The quadratic mean diameter of particulates began to increase gradually then stabilized in the range of 8.97~10.68 μm. The dissolution rate of TOC and DOC gradually decreased. DOC dissolution rate was less than the TOC dissolution rate. The distribution diagram of dissolved organic matter (DOM) showed that the degradation of macromolecule DOM mainly concentrated in the first 5days. All of the macromolecule DOM with molecular weight between 1.6×109~1.9×109Da degraded to DOM between 5×104~4×106Da. The distribution of DOM changed a little after the 5th day. It was recommended that hydrolysis time could be shortened to 5 days during a two-phase anaerobic digestion of vegetable waste.
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Received: 01 December 2013
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