Toxic effect of sulfur compounds on anaerobic biogranule

The effects of sulfide, sulfite and sulfate on degradation of volatile fatty acid (VFA) in UASB process have been studied by using serum bottle assay and septage–leachate acclimated biogranules. The relative toxicity of the compounds towards methane production and degradation of total VFA varied as SO 4 2−S>S 2−>SO 3 2−S and SO 4 2−S>SO 3 2−S>S 2−, respectively. The difference of this order shows the importance of choosing monitoring factor in evaluating the effect of sulfur compounds on a UASB system. For the individual VFA the effects of sulfur compounds depended on the types of VFA. The VFA-degrading activity of anaerobic biogranules was decreased by 50% when 34, 26 and 20 mg of S 2−, SO 3 2−S and SO 4 2−S were added to each gram of biomass, respectively. A comparison of the toxicity-resistance between two different anaerobic biogranules that acclimatized with septage–leachate mixture and septage was also made. In the presence of the leachate, the toxicity-resistance of biogranules was not weakened to sulfide and sulfate but was enhanced to sulfite.