The release of hydrogen sulfide (H2S) during sludge drying is a major environmental problem because
of its toxicity to human health. A series of experiments were performed to investigate the mechanisms
and factors controlling the H2S release. Results of this study show that: (1) the biomass and activity of
sulfate-reducing bacteria (SRB) in sludge were the major factors controlling the amount of H2S release,
(2) the sludge drying temperature had an important effect on both the extent and the timing of H2S
release from the sludge, and (3) decreasing sludge pH increased the H2S release. Based on the findings
from this study, a new system that integrates sludge drying and H2S gas treatment was developed, by
which 97.5% of H2S and 99.7% of smoke released from sludge treatments was eliminated.