Factor analysis of H2S emission at a wastewater lift station: a case study.

Odor and corrosion are common problems in domestic wastewater collection, transportation, pumping, and treatment processes. Based on the comparison among odorous compounds and onsite observations at a wastewater lift station, H2S is more likely to have caused the odor and corrosion problems than methanethiol and other organic sulfides. The field data from both air and wastewater quality monitoring demonstrated that more H2S (1 ppmv) was formed at a more negative redox potential, lower pH, and a higher temperature of wastewater. Since the lower detection level of most current analytical techniques is much greater than human's smell and the reference concentration for adverse health effects, automatic monitoring on the threshold of H2S formation provides a mechanism to trigger control techniques only when necessary for cost saving purposes. Based on Gibbs free energy, a more negative redox potential is required to form H2S with an increase in pH and a decrease in temperature and SO 4(2-) concentration. However, pH effect is more significant than both temperature and SO 4(2-) concentration for H2S formation. It is recommended that H2S control techniques be started when the redox potential is below -44 mV, the pH is lower than 5.6, and the temperature is higher than 11.5 °C to control H2S below the reference concentration. Corroded concrete particles were examined by X-ray diffraction, which showed that the dominant crystal form was quartz.