Experimental facilities comprising 1.8 km of pipeline, 100 mm in diameter and pumping equipment, were installed in a wastewater treatment plant and operated continuously for more than one year to clarify the main factors governing hydrogen sulfide generation in pressure mains. The effects of temperature, organic matter, and sulfate on sulfide generation rate were investigated based on observed values. The sulfide generation rate depended significantly on wastewater temperature. It was confirmed not empirically but experimentally that the effect of temperature (T) was expressed by (1.065)T-20. In respect of organic matter, it is considered that there is a little effect of organic matter concentration on sulfide generation rate when the fluctuation of soluble organic matter concentration is slight. However, based on observed values, it was found that sulfide generation rate clearly depended on sulfate concentration when the biofilm was rather thick like these experiments. Also, partial penetration of sulfate into biofilm was confirmed using a biofilm model. Furthermore, biofilm model as a sound method for predicting sulfide generation rate was discussed.
