AWWA JAW62276

This research investigated how sulfate-reducing bacteria (SRB) influences the mineralogy of iron-corrosion scales. Microbiological activity in the distribution system is well known and recognized as a potential health-related concern. The effect of bacteria on corrosion has also been studied, however, the extent to which SRB actually affect corrosion and degradation of distribution system material in real distribution systems had not been well documented. Iron-corrosion scales were collected from a surface water system and a groundwater system, each with relatively high sulfate concentrations. Results showed that reduced sulfur was a significant component of all scales studied. Elemental sulfur and iron disulfide dominated sulfur species in all of the analyzed scales. Other important iron minerals found were goethite and lepidocrocite. However, magnetite, considered an important mineral in protecting iron pipes from extensive corrosion and iron release, was present only in the iron scales collected from the surface water system. The article highlights the degree to which microbiologically induced corrosion affects pipe material degradation and corrosion scale buildup, which in turn affects the hydraulics of the distribution system, material replacement, and other operating parameters. An understanding of these issues and an awareness of the conditions that favor microbiological corrosion of iron pipe will help water providers determine any measures needed to improve their distribution system maintenance programs and preserve water quality. Includes 37 references, 5 tables, 4 figures.