Biogenic Sulphuric Acid Attack of Concrete Sewer Pipes: A Prediction of the Corrosion Rate

Abstract

Biogenic sulphuric acid corrosion is a phenomenon which occurs mainly in sewer pipes. The process consists of four stages: the reduction of sulphate to sulphide; the transition of sulphide to hydrogen sulphide gas in the sewer atmosphere; the re-oxidation of the sulphide gas to sulphuric acid in an oxidizing environment of the sewer pipe and finally concrete attack by sulphuric acid. Different models are developed to predict the sulphide formation and the corrosion rate. The model of Pomeroy, according to which the rate of sulphur production and the rate of corrosion can be calculated, is used in this paper. Different parameters are taken into account and case studies are described. Comparison of the calculated corrosion and the measured corrosion indicates the accuracy of the formula. In addition, a sensitivity study is carried out on the formulae to distinguish the influence of the different parameters. A realistic variation of the different parameters is made, based on measurements at the inlet of purification plants. The most influencing parameters for the model were the temperature, the BOD-content and the pH-value of the waste water, the depth of flow and the detention time.