| Bio-hydrogen production from food origin waste is a food waste bio-treatment technology which can solve pollution problem, but also produce clean fuels according with the concept of sustainable development. Currently, some problems exist in the biological hydrogen production, such as low efficiency of hydrogen-producing, low percentages of hydrogen. To improve capacity of hydrogen production, the bio-hydrogen fermentation system composed of rice slurry as leavening, aged refuse as additive was studied on the lab scale, to study metal ions on hydrogen production of the system. Single and combined effects of four kinds of metal ions (iron, magnesium, nickel and molybdenum) on hydrogen production of the system were investigated using second order regression current rotation design and statistical methods. The results indicated the total effect, mutual influence and principal factor effect of various metal ions coexistence. It is helpful to establish biological dedication mathematical model.The results obtained are as follows:1. The single factor experiments were taken by adding different concentrations of Fe, Mg2+, Ni2+ and Mo6+ to the bio-hydrogen fermentation system individually. Hydrogen yield of all experimental groups were higher than that of control group. The best ion concentration of Fe, Mg2+, Ni2+ and Mo6+ were 750mg/L,225mg/L,0.5mg/L and 0.4mg/L, and the hydrogen yield increased by 188.17%,659.19%,235.68% and 279.60% compared to that of the control group, respectively. According to the fitting results, adding different ion concentrations of iron, magnesium, nickel and molybdenum can improve the maximum hydrogen production potential to varying degrees, shorten the fermentation lag time, and promote hydrogen production of the bio-hydrogen fermentation system. 2. The effects of mixture of each two ions of Fe, Mg2+, Ni2+ and Mo6+ at different concentrations were conducted using second order regression current rotation design. Six regression models about cumulative hydrogen production and ion concentration had been established by software SPSS 15.0, The fitting results of mixture of Fe and Mg2+ and mixture of Fe and Ni2+ were better than that of other mixtures (R:0.810-0.844,P<0.01). Combined influence of different ions and principal factor effect of different mixtures were found to be different at different ion concentration intervals.3. The influences of mixture of each three ions of Fe, Mg2+, Ni2+ and Mo6+ at different concentrations were carried out. Three regression models between about the cumulative hydrogen production and ion concentration had been built by software Spss 15.0. The fitting results of mixture of Fe, Mg2+ and Ni2+ was better than that of other mixtures (R:0.921, P<0.01). Combined influence of different ions was found to be different at different ion concentration intervals.4. The combine action of the four metal ions was analyzed by statistical method. The results showed that hydrogen production were different at different ion concentrations and the combined effect was changed with different ion concentration intervals. According to principle component analysis, Fe had more influence on cumulative hydrogen production, next was Mg2+, Mo2+ and Ni6+. Based on experiment results, the regression models between the total hydrogen production and concentration had been drawn out, which had been tested ordinary significance and common goodness of fit. On the total hydrogen production is the single greatest impact on quality of iron, followed by magnesium, and the least impacts are molybdenum and nickel.
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