Study On Bio-hydrogen Production Using Kichen Wastes Via Anaerobic Fermentation

The huge increasing of the amount of the kitchen waste, which come up with the improvement of living standard, has been affecting the environment more and more seriously, which will threat people's health.As a result, more and more attentions are paid on how to deal with the kitchen waste rapidly and effectively.The hydrogen, one of the cleanest energy sources,which makes nothing after burning can replace the fossil fuel perfectly. And hydrogen production through anaerobic fermentation is the most feasible way. Hydrogen production using kitchen wastes were decomposed by hydrogen-producing bacteria into organic acids (acetic acid, butyric acid, etc.), ethanol, CO₂ and H₂.Because of the using of the H₂ and H⁺ by Methanogens, which are made in the acidification phase, some pretreatments should be done on granular sludge to inhabit the activity of CH₄ producting, and get enough hydrogen. Initial pH, fermentation temperature, carbon nitrogen ratio as well as the metal ions on hydrogen content, the accumulation gas production and the dehydrogenase activities were also investigated in the experiment.The last step of the study was purifying the bacteria in the hydrogen production systerm.And two strains of bacteria, which were identified by 16s rDNA, were found that they have different effects on hydrogen production.The results indicated that: 1. Different pretreatment methods have the same effects on inhabiton of CH₄ producing activity. Comparing with other treatments, the heat treatment (120℃15～25min or 80℃～100℃30min) made the granular sludge the most active on hydrogen production, that the content of the hydrogen was 54%.Furthermore, the condition of 120℃25min heating treatment caused the highest dehydrogenase activity, which indicated that the spore in sludge was activated significantly. 2. The optimum conditions of activity of hydrogen producting were T=32±1℃, initial pH=6.5～7.0, C/N=20:1, CNi²⁺=267.6 ug/gTS, CFe²⁺= 49496.0 ug/gTS. Metal ions affecting methane production is in the following order: Ni²⁺>Fe²⁺>Mg²⁺. And the comparison of dehydrogenase activities show that it was not completely matchable on the optimum conditions between the activity of hydrogen producting and the dehydrogenase activity. 3. Two of the bacteria through isolating and purifying from the reaction system, identified by 16srDNA,were Bacillus licheniformis and Escherichia coli. The first one promoted the formation of anaerobic environment, and strengthen the effect of the hydrolysis of substrate; the second one, which also promoted the formation of anaerobic environment, increased the density of hydrogen-producing bacteria of the system, which made the hydrogen production more efficient.