New Findings in Hydrogen Sulfide Related Corrosion of Concrete Sewers

This paper summarizes major findings of a long-term study of hydrogen sulfide gas (H₂S) adsorption and oxidation on concrete and plastic sewer pipe surfaces. The processes have been studied using a pilot-scale setup designed to replicate conditions in a gravity sewer located downstream of a force main. H₂S related concrete corrosion and odor is often observed at such locations. The experiments showed that the rate of H₂S oxidation was significantly faster on concrete pipe surfaces than on plastic pipe surfaces. Steady state calculations based on the kinetic data demonstrated that the gas phase H₂S concentration in concrete sewers would typically amount to a few percent of the equilibrium concentration calculated from Henrys law. In plastic pipe sewers, significantly higher concentrations were predicted because of the slower adsorption and oxidation kinetics on these surfaces. Finally, the paper demonstrates how the kinetic data can be used for prediction of concrete corrosion in real sewer systems based on H₂S measurements from a conventional gas detector.