Production Of Hydrogen By Wastewater Sludge Using Anaerobic Fermentation In A Pilot Scale Reactor

The aim of this study is to investigate the production of bio-hydrogen, via dark anaerobic fermentation in a pilot scale reactor under batch conditions, using a mixed microflora. As inoculum, anaerobic digested sludge, collected from municipal wastewater treatment plant, was used after being pre-treated with HCl 1N for 24h (pH 3) in order to inhibit the methanogenic bioactivity. As a source of carbon, sucrose at high concentrations (100 g/l) dissolved in a medium containing salts and micronutrients was employed. During fermentation temperature was maintained at room conditions (20°C), pH ranged from 7.2 to 5.2, due to the formation of Volatile Fatty Acids (VFAs), that showed a butyrate-type fermentation. The reactor produced approximately 70 l of gas containing hydrogen (46%) and carbon dioxide (54%) with a global yield of 0.32 mol H2/mol sucrose, whereas no H2S or CH4 was detected, suggesting that acid pretreatment plays an important role in the elimination of methanogenic bacteria. Formation of VFAs, sucrose concentration and biomass concentration in terms of CFU/ml of Clostridium spp. were reported at different times. The investigation of these parameters led to a kinetic study for the description of the dark anaerobic fermentation process, in order to obtain data for future experiments for the production of biohydrogen with a continuous stirred tank reactor (CSTR).