Producing hydrogen from wastewater sludge by Clostridium bifermentans

Excess wastewater sludge collected from the recycling stream of an activated sludge process is biomass that contains large quantities of polysaccharides and proteins. However, relevant literature indicates that the bio-conversion of wastewater sludge to hydrogen is limited and therefore not economically feasible. This work examined the anaerobic digestion of wastewater sludge using a clostridium strain isolated from the sludge as inoculum. A much higher hydrogen yield than presented in the literature was obtained. Also, the effects of five pre-treatments—ultrasonication, acidification, sterilization, freezing/thawing and adding methanogenic inhibitor—on the production of hydrogen were examined. Freezing and thawing and sterilization increased the specific hydrogen yield by 1.5–2.5 times to that of untreated sludge, while adding an inhibitor and ultrasonication reduced the hydrogen yield.