Release of organic sulfur as sulfur-containing gases during low temperature pyrolysis of sewage sludge

This study reports the release of five sulfur-containing odorants (H2S, SO2, COS, CS2 and CH3SH) during the pyrolysis of sewage sludge. Pyrolysis experiments using both raw sewage sludge and seven sludge samples loaded with various organic sulfur compounds were performed to determine the effects of the type of organic sulfur on the release of sulfur-containing gases. It was observed that the formation of H2S, the predominant odorant, significantly increases at temperatures above 150 °C. Aliphatic and aromatic sulfur compounds were found to be the two main organic sulfur sources for the release of sulfur-containing gases. The release of sulfur-containing gases from aliphatic sulfur greatly increases at 250 °C, whereas significant sulfur-containing gases are released from aromatic sulfur at relatively high temperatures of 350-450 °C. It was also observed that the presence of sulphonic acid and thiophene in sludge does not significantly affect the release of sulfur-containing gases.