Optimization Of Bio-hydrogen Production Process From Dark Fermentation By Anaerobic Sludge And Microorganism Loading Analysis On Different Packings

During the last several decades,the energy crisis and environemental pressure caused by industrial expansion and sharp population growth have accelerated the development rate of the renewable energy.As a best kind of clean energy,hydrogen is considered to be the most development-valuabe alternative energy.To overcome the obstacles through the hydrogen production process from fossil fuels,biohydrogen production technology has become to be a focus during the hydrogen production technology studies.Especially the biohydrogen production technology by the dark fermentation drew great attention of scholars inside and outside the country because of its high industrial application prospect.In this research,the hydrogen production bacteria were screened after the sludge domestication and bacteria enrichment.It was identified to be one kind of themophilic bacteria named bacillus cereus whose suitable growth pH was 7.0,at which situation obtained the optimum hydrogen yield of 1.76 mol H2/mol glucose.By optimizing the medium,the optimum concentration of the synthetic waste water was 16.4g COD/L;C/N ratios changed by adjusting the concentration of carbon and nitrogen sources.The results showed that when glucose concentration was constant at 20g/L,the C/N ratio that was suitable for hydrogen production was ranged from 11.43 to 45.72.Three different particles of foam silicon carbide,silica gel and activated carbon were researched to fix bacteria.It was shown that the foam silicon carbide was the best particle utilized as the bacteria fixing carrier.Compared with the silica gel particles and activated carbon,the bacterial concentration fixed on the silicon carbide was 2.22 fold and 2.38 fold high,respectively.Moreover,SEM picture of the foam silicon particles indicated that the bacteria were fixed by formating bacterial biofilm on the particles.Then the SiC structured packings were applied in an up-flow packed bio-reactor to produce hydrogen.The hydrogen production rate was 1.67 fold to a blanket UASB reactor without any packs at the C/N of 45.72,HRT value of 3.33 h.The bacterial accounts fixed on the SiC packing was about 50 fold higher than that in the solution of the reactor.By analysing the effluent constitution and the identified bacteria fixed on the SiC packing,it proved that the hydrogen production through dark fermentation process was one kind of mixed fermentation type lead by the butyric acid fermentention way.