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Polymer electrolyte membrane (PEM) degradation in electrolysis mode is simulated through a Fenton model that includes all major involved electrochemical reactions. Supportive experimental investigations on the effect of hydrogen peroxide and iron impurities are carried out in an ex-situ set-up, where the results are utilized to fit model parameters. The experiments reveal a high dependence of fluoride emission on iron concentration, which catalyzes the reaction, and identifies hydrogen peroxide as a necessary precursor for destructive hydroxyl radical formation. Simulations of in-situ operation reveal * Corresponding author, (+45) 50 25 10 31

The formation and fate of sulfide in a force main and a downstream‐located gravity sewer were investigated in an extensive field study. Sulfide formation in the force main was significant. However, during 14 minutes of transport in the gravity sewer, the sulfide concentration decreased 30%, on average. An application of a conceptual sewer process model for simulating the formation and fate of sulfide was demonstrated. Overall, the model predicted that approximately 90% of the decrease of the sulfide concentration in the gravity sewer was the result of sulfide oxidation and that only a small fraction entered the sewer atmosphere, causing odor and corrosion. Even so, the model predicted concrete corrosion rates of up to 1.2 mm/y in the gravity sewer section.

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Abiotic and biotic oxidation of hydrogen sulfide related to concrete corrosion was studied in corrosion products originating from a sewer manhole. The concrete corrosion products were suspended in an acidic solution, mimicking the conditions in the pore water of corroded concrete. The removal of hydrogen sulfide and dissolved oxygen was measured in parallel in the suspension, upon which the suspension was sterilized and the measurement repeated. The results revealed the biotic oxidation to be fast compared with the abiotic oxidation. The stoichiometry of the hydrogen sulfide oxidation was evaluated using the ratio between oxygen and hydrogen sulfide uptake. The ratio for the biotic oxidation pointed in the direction of elemental sulfur being formed as an intermediate in the oxidation of hydrogen sulfide to sulfuric acid. The experimental results were applied to suggest a hypothesis and a mathematical model describing the hydrogen sulfide oxidation pathway in a matrix of corroded concrete.