(283h) Bio-Hydrogen Production By Mixed Bacteria From Anaerobic Sludge With Different Combined Pretreatment Methods

Microbial hydrogen production by anaerobic bacteria has been extensively investigated since hydrogen is considered to be a future clean source of energy. Dark fermentation systems offer an excellent potential for practical application with emerging hydrogen and fuel cell technologies. Many investigations focus their attention on the pure bacteria, and a number of known bacteria have been used to produce hydrogen gas^[1,2,3,4]. But the process is limited by the distribution and immobilization of the bacteria. So there are also some studies on the anaerobic sludge which is used as the source of the mixed bacteria during the dark-fermentation. However, the hydrogen yield rate is low (Currently fermentative processes produce 0.48 to 1.63 mole of hydrogen per mole glucose)^[5,6,7].

In order to enrich hydrogen producing bacteria and increase the hydrogen yield, four combined pretreatment methods including heat+ acid, heat+ alkali, acid+ heat and alkali+ heat were performed on the seed sludge in this paper. During the dark fermentation, the theoretical hydrogen yield is 4mol H₂/mol glucose when the process is acetic-acid type fermentation. Generally, 25-50% of the theoretical hydrogen yield can be obtained from sugar fermentation with mesophilic temperatures and moderate microorganisms^[8,9,10,11]. Results showed that hydrogen yield increased greatly from 1.16 mol H₂/mol glucose (heated only) to 1.867 mol H₂/mol glucose through the optimization of the combined pretreatment methods. And the highest hydrogen concentration reached 85% at 80^oC for 40min at pH3.0 (heat+acid).

Since the process of photo-fermentation can utilize the volatile fatty acids (VFAs) produced by the dark-fermentation and realize continuous and stable H₂ production. In this study, the pretreated bacteria were continually enriched with the production by the dark-fermentation. Then the enrichment cultures were carried out the photo-fermentation, the hydrogen yield could reach 6.24mol H₂/mol glucose.  

Reference

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