Oxidation of biologically produced elemental sulfur under neutrophilic conditions

BACKGROUND: Previous research on a biotrickling filter for the removal of high loads of H 2 S showed that accumulation of elemental sulfur (S 0 ) when dealing with high H 2 S concentrations could lead to reactor clogging. Since S 0 can also serve as substrate for sulfur‐oxidising bacteria, this study investigates the biological oxidation of S 0 as a remediation strategy. RESULTS: Results indicated that biological oxidation of S 0 inside a clogged biotrickling filter occurred at a comparable rate to those reported for stirred tank reactors. When biologically produced dried and powdered S 0 was manually added as a substrate in stirred tank reactor experiments, significantly lower S 0 oxidation rates were found compared to those for biological S 0 freshly produced in situ . It was speculated that either the powdered S 0 particle size or the surface properties hindered S 0 bioavailability even in a well‐stirred environment. Respirometric experiments with the same powdered S 0 and acetone‐dissolved S 0 confirmed that biological oxidation of S 0 was basically limited by the solid S 0 bioavailability. CONCLUSIONS: Therefore, results showed that S 0 oxidation basically depends on S 0 bioavailability and that Sulfate volumetric production rates as high as 3.48 mmol SO 4 2− h −1 L −1 can be achieved inside a clogged biotrickling filter probably due to the high biomass retention capacity. Overall, the results indicate that biological oxidation of S 0 can be considered a suitable strategy for unclogging bioreactors clogged with S 0 . Copyright © 2010 Society of Chemical Industry