Abstract
BACKGROUND: In anaerobic wastewater treatment processes, the presence of sulfateβreducing bacteria (SRB) produces H~2~S. Many techniques are being used to remove H~2~S from biogas to obtain H~2~Sβfree biogas but none of those are cost effective or efficient enough to remove the H~2~S completely. The objective of the present study was to introduce some changes/modifications to the process parameters of the wastewater treatment operation to eliminate SRB from the system.
RESULTS: The growth of SRB was found to be completely suppressed under thermophilic conditions (55 Β°C) but not at 37 Β°C. H~2~Sβfree biogas containing 56.5% methane was obtained at 55 Β°C after 180 days of treatment. The effect of higher concentrations of volatile fatty acids (VFAs) on the growth of SRB and methanogens at 37 Β°C and 55 Β°C were also studied. At higher VFA concentrations, SRB outgrew the methanogens at 37 Β°C but at 55 Β°C the situation was found to be reversed. For continuous operation at 55 Β°C and low dilution rate (0.0075 h^β1^), SRB was suppressed and biogas having 29% methane but free of H~2~S was obtained.
CONCLUSION: Operating the reactor at high temperature (550C) and low hydraulic retention time (HRT) can result in the production of H~2~Sβfree biogas, with a high concentration of methane. Copyright Β© 2008 Society of Chemical Industry