Design Your Collection System to Reduce Risks of System Failures Due to Hydrogen Sulfide Gas Formation

Traditional design approach of determining the pipe size based on peak flow without taking into consideration odor formation potential during minimum dry weather flows as well as peak flows increases the risks of exposure to odors and corrosion failures due to H2S gas formation. It is important, therefore, to limit the conditions that promote the formation of H2S gas through good design practice. In this work, the basic steps involved in calculating the parameters that estimate the magnitude of H2S gas formation potential in the sewer system and the criteria for selecting the most desirable design were outlined. Using the basic steps and selection criteria outlined, a spreadsheet was set up as a design tool for estimating those parameters based on hydraulic characteristics of the pipe and the quality of the wastewater being conveyed. As an illustration, the developed design tool has been applied to a development of 500 acres with a population of 3,750 people to study the impact of flow variation on H2S gas formation potential, and the appropriate pipe size and slope for the gravity interceptor sewer was selected to minimize the potential for H2S gas formation.