| Energy shortage and environmental pollution problems had forced the humanity to find new clean energy.In recent years,hydrogen was regarded as one of the most promising energy because it has the advantages of non-pollution,renewable production,higher combustion heat value compared with the traditional fossil fuels.Because biological hydrogen production can transform organic matter into hydrogen with microorganism,so it has the features of moderate reaction conditions,abundant raw materials,lower energy consumption,non-pollution,etc.In particular,Hydrogen production with photosynthetic bacteria has effectually combined the use of solar energy,hydrogen production and pollution control technology form a whole,so it solved the problem of energy shortage with relatively low energy consumption,reduced the environment pollution resulting from the use of fossil fuels.The researches of hydrogen production with photosynthetic bacteria started rather late,many correlational studies of hydrogen production were still in its early stages.Although there are many advantages in hydrogen production with photosynthetic bacteria,relative to other biological hydrogen production technology,but photosynthetic bacteriaes have many classification,various metabolic pathway and influence factors,therefore,hydrogen productivity of light fermentation hydrogen production remains lower level at present.The reported studies of hydrogen production with photosynthetic bacteria were performed in batches in the laboratory,but experiment on continuous hydrogen production was very few.The volumetric of photobioreactor was difficult to expand because the attenuate of light intensity occurred in the fluid of photosynthetic bacterial.At the same time,the concentration of bacterial in continuous hydrogen production was littler due to strain slow-growing.These difficulties had seriously hindered the technical transformation of hydrogen production by photosynthetic bacteria in the lab into practical production.In this paper,first of all,photosynthetic bacteriaes were separated from the activated sludge,then,the characteristics of hydrogen production with new strains of photosynthetic bacteria were studied using a variety of organic matters.Second,based on the reviews on the development of photobioreactor,the new built-in light source photobioreactor with a larger volume was designed.After combined the technology of immobilized bacteria,the stability of hydrogen production was improved in continuous hydrogen production.Finally,a higher efficiency experiment on hydrogen production of PSB with glucose as the main substrate had been studied in continuous hydrogen production.Paper main research results obtained are as follows:?1?Mixed liquid of PSB was collected firstly from wastewater plant in Xi‘an by selective enrichment techniques for phototrophic bacteria,then,Six purify strains of purple non sulfur bacteria was isolated using agar plates embedded in paraffin.The most strain of H2 production efficiency was identified as number PS-6 by comparative test of producing hydrogen.Finally,according to the conventional bacterial analysis experiment,such as bacterial morphological characteristics,physiological and biochemical characteristics,etc.,and based on the 16 S rDNA sequencing result,we could make sure that PS-6 was Rps.Palustris.?2?Lag phase of hydrogen production was about 12 h with Photosynthetic bacteria using glucose as a substrate for H2 production.The glucose was fermented to small molecule organic acids and alcohols,according to the order of the concentration from big to small,the main products are acetic acid,ethanol,butyric acid and propionic acid.Experiments showed that ammonia nitrogen and sodium glutamate can all be used as nitrogen source for hydrogen production by Rps.Palustris PS-6 with glucose.Maximum hydrogen yield was 0.893 mol H2/mol glucose under the best conditions,such as 45.0mmol/L glucose concentration,3.0mmol/L glutamate dosing,and light intensity for 4000 lux.Hydrogen is present from 37% to 43% by volume in the mixed gas.Experiments showed that sodium glutamate was better nitrogen source for hydrogen production,but ammonia nitrogen was not used as nitrogen source for hydrogen production by Rps.Palustris PS-6 with small molecular organic acid.Lag phases of hydrogen production were about 60 h,84h,48 h and 36 h using acetic acid,propionic acid,butyric acid,lactic acid as a substrate for hydrogen production,respectively.Maximum hydrogen yield was 1.632 mol H2/mol acetic acid when acetic acid concentration is 45.0mmol/L,the dosing of glutamate is 7.0mmol/L,and inoculation proportion is 15% by volume.Hydrogen is present from 77% to 83% by volume in the mixed gas.?3?In this work a new type of interior optical fiber illuminating reactor was developed for H2 production to solve the problem of luminous intensity attenuation in the center portion of a reactor.The effective volume of reactor is 4000 ml?Height 600 mm,diameter 100 mm?,and 25 side glowing optical fibers were set up along the axis direction parallel in the reactor as transmission light sources.The uniform light intensity was achieved at different locations of the reactor,and reached 4000 lux.Results of experiments show that the interior optical fiber illuminating reactor produces H2 more efficiently and productively than the exterior light source reactor,with the cumulative H2 production,the maximum H2 production rate and H2 yield increased by 11.3ml/l/h and 22.3%,respectively,using glucose as the sole carbon substrate for the Rhodopseudomonas palustris SP-6.In this work an immobilization technique was used to enhance the stability of a continuous hydrogen production process with attached photosynthetic bacteria.The stability of the product of continuous hydrogen was realized by immobilizing Rhodopseudomonas palustris SP-6 on the surface of powder active carbon?PAC?.After adding the dosage of 2.0g/L PAC,the continuous steady operation of H2 production gave a high H2 yield of 1.398 mol H2/mol glucose and an average H2 production rate of 35.1ml/L/h illuminating with a single interior optical fiber light source using glucose as the sole carbon substrate.Meanwhile,a higher H2 yield of 1.495 mol H2/mol glucose and an average H2 production rate of 38.7ml/l/h were attained illuminating with a compound lamp in the continuous H2 production for 20 days.?4?According to the produce hydrogen characteristics of photosynthetic bacteria with different organic matters,hydrogen production by photosynthetic bacteria is proposed to integrate two phase hydrogen production with glucose as the substrate into an efficient first-order hydrogen production.Through activating cultivation of photosynthetic hydrogen production strain and optimizing reaction conditions,experiment of continuous first-order hydrogen production had been implemented by Rps.Palustris PS-6 with glucose as substrate.Continuous operations were fairly stable and efficient,and the highest hydrogen yield,4.6 mol H2/mol glucose,was obtained while using the dosage of sodium glutamate 0.7g/l,initial glucose concentrations 9.0g/l,and operating at 84 h HRT in a single stage system. |
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