| The emission of huge amount of carbon dioxide lead to the global warming under the rapid development of economy, scientific technology and industrialization. It is urgent to seek a clean, highly efficient and renewable energy when we realize global warming can cause a series of severe environmental issues, plus the demand for energy is increasing. Hydrogen energy become the novel substitute energy due to its reproductiveness, no pollution after burning and other properties. Utilization of hydrogen energy can benefit sustainable development from previous low-carbon to present zero-carbon environmental protection.This study investigated the effects of load impact on the biohydrogen production system and that of controllable parameters used from sludge inoculation cultivation to realizing highly efficient hydrogen production, various substrates (molasses, red sugar and potato) on this system and microoganism morphology mutation.Studies had shown that, in the early stage of the biohydrogen production reactor starting up, the stability of biohydrogen production system was investigated by changing substrate loads. When the substrate concentration varied from5500mg/L to7400mg/L, the maximum value of gas and hydrogen production were25.39L/d and11.39L/d, respectively. When the system reached a stable state of hydrogen production, the maximum yield of hydrogen production were0.65L/d for the molasses and1.95L/d for the red sugar with their concentrations of3000mg/L, respectively. At the same time, the proportions of propionic acid and butyric acid decreased significantly, which changed from25.7%and15.4%to11.8%and9.47%. The fermentation type converted to a stable ethanol-type fermentation from the mixed acid fermentation.The activated sludge in the manmade brown-sugar water serving as the substrate was used to produce hydrogen. At first, we tamed ethanol-type fermentation population which could produce hydrogen through the continuous stirred tank reactor (CSTR) under the certain conditions. The sludge aerobic pretreated for three weeks was inoculated to the reactor after strengthened with the70℃water bath for30min. And then we did some researches about strengthening the hydrogen-producing efficiency and metabolic processes of sludge by heating pretreatment. After that, we compared some parameters before and after being strengthened in the system, including its ability of producing hydrogen. The activity VSS/SS of the enhanced sludge was for55%at the first time, the result showed that the gas and hydrogen production of system after the first consolidation increased from5.39L/d,2.41L/d to6.90L/d,3.32L/d, strengthened1.28and1.38times for the before, respectively. The rate of the liquid end products as acetate, ethanol, propionic acid, butyric acid proportion respectively increased by 25.5%,31.4%,22.4%,56.5%. After the second enhancement of sludge, the activity VSS/SS of the enhanced sludge was for56%. The gas and hydrogen production increased to12.52L/d and5.47L/d, respectively. The hydrogen content was as high as51.9%, and the total of VFAs reached to the maximum value1977.32mg/L. The result indicated that the enhancement of sludge was conducive to higher hydrogen production in anaerobic sludge system, and the running system could be stable again in a short time.In the batch culture, studies have showed the influence of the hydrogen production by loading and substrate changing. The amount and concentration of (molasses, brown sugar and wastes-sweet potato) was3500mgCOD/L, after30h fermentation, the system achieved for2mL,8mL,2.4mL and0.015%,0.28%,0.18%, respectively. While the reactor of sweet potato as the substrate operated for more18h, hydrogen production was almost ceased and hydrogen content decreased minimum value. The amount of liquid the end product was consistent with the gas production trends. The maximum value when the red sugar fermented was for11083.29mg/mL, while the sweet potato fermented the minimum amount of total volatile acids was about10,000mg/mL. The end product of each reaction was mainly acetic acid and propionic acid, and the total content accounted for more than80%of the total liquid end products and formed the propionic acid type fomentation. When the substrate of the sweet potato changed from2500mgCOD/L to7000mgCOD/L. In the period, the system pH reduced rapidly and ORP suddenly increased. The amount of gas production and liquid end products tend almostly verged to zero. The result showed that fermentation micro-organisms have some selectivity on the substrate. The interspecific competition is different which different substrate caused. The experiments showed that the substrate-sweet potato is not conducive to ferment for hydrogen production. |
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