Study On Hydrogen Production And Biodegradation Characteristics In Biofilm Photobioreactor

Along with the economic development and the increasing requirement of energy to human being, mineral fuel as the major energy sources, such as coal, petroleum, natural gas, etc. which conservations are decreasing continuously, according to present consumption speed of energy sources, the crisis of mineral fuel is faced with inevitably. Thereby, the exploiture of clean energy sources is a general trend. Hydrogen as one kind of renewable energy sources, which is inexhaustible, and it has the following advantage: clean, low density, high caloric value, high utilization rate and used abroad. The technique of biological hydrogen production has mild reacting condition, low energy consumption, and it could solve problems between energy source and environment appropriately and advance development of economy and environment harmoniously, biological hydrogen production has turn into a popular exploring research in the world. Furthermore, hydrogen production by photosynthetic germs has many advantages such as high purity degree of hydrogen production, broad responds to solar spectrum, faster production of hydrogen than alga, higher utilization rate of energy than non- photosynthetic germs, and higher transforming rate, which turns solar energy into hydrogen energy by organic waste water. Hydrogen production, utilization of solar and de-organic waste water were coupled altogether, so hydrogen production by photosynthetic germs was taken as a prospective way to get green hydrogen.In the present study, the experiments on the bio-film startup performance and influential ingredients for the hydrogen production in the reactor with beadings were investigated. According to porosity medium theory, a theoretic model was established for describing substrate transport processes and animalcule biochemical reaction, and at the same time another heat production by bio-film metabolism model also established for describing metabolic heat production and transfer in the reactor. The main research production as follows:①The microorganism from collection of the living earth was cultivated and domesticated, which bacterial strain with high toluene degradation capability was received. The bacterial strain belongs to Rhodoseudomonas palustris.The H2 yield can reach to 4.105 mmol H2/(100ml culture medium).②The experiments on the start-up of hydrogen producing reactor were conducted which firstly obtained the evaluating status for start-up accomplished. The experimental results show that the start-up progress of hydrogen producing reactor included bio-film formation period, development period, and stabilization period. The similar change tendency of OD600nm of circulation liquid, the production of hydrogen in the reactor and the consumption of substrate can be used to evaluate the start-up status of hydrogen producing reactor. The inlet substrate concentration, OD600nm of circulation liquid, and liquid flow rate had significant effects on the bio-film formation during the start-up of hydrogen producing reactor.③The experiment for hydrogen production in the reactor withφ4 mm beading was conducted. The main effect factors for hydrogen production in the reactor were investigated. The results reveal that under different illuminations the most proper substrate concentration is 0.12mol/l, the exorbitant substrate concentration could restrain hydrogen production. Under different spectrums, the best intensity of light is 5000lx for Rhodoseudomonas palustris, more or less than 5000lx would go against hydrogen production. And it was found that at 25℃hydrogen producing rate would on the top in the reactor, the much higher or lower temperature would go against hydrogen production too, at 10℃or 40℃hydrogen production would decrease to zero. When PH of the circulation liquid is 7, the hydrogen producing rate would on the top, when PH of the circulation liquid is 4 or 9, the production would stop.④The steady reactor theoretical model of hydrogen production by photosynthetic germs was established with simplifying the porous packed bed to a series of parallel flats covered by the bio-film, in which conservation of mass of liquid flow was build, and mass transport and biochemical reaction kinetics were taken. The results of model are basically in agreement with the experimental data.⑤Based on biochemical metabolism theory and the theory of light energy transmission, the metabolized heat generation model of hydrogen production by photosynthetic germs is proposed firstly.