AWWA WQTC58973

After a detailed investigation on the failure of copper water service pipes in the Brown Deer, Wisconsin water distribution system, microbiologically influenced corrosion (MIC) was found to be the cause. Typical characteristics of MIC are explained in this report and include: jagged pit morphology; presence of microorganisms only in corrosion debris and pits; initiation of corrosion at the extreme of the water system, especially in areas of high water age; initiation of corrosion at low points in pipe lines; inadequate disinfection levels in the water at the entry points to the system; further reduction of disinfection levels in the corroded areas of the system; and, a water treatment history that points to an increase in nutrients for microorganisms just before pipes began to fail. To remediate Brown Deer's problem of copper pipe biocorrosion, the following actions were taken: a procedure for monitoring the distribution system was created to routinely track disinfection levels, ammonia levels, heterotrophic plate count (microorganisms), and other parameters of special interest; disinfection boosting facilities are being planned with a fast-track design for the first facility; and, system cleaning was continued and extended. The Brown Deer Water Utility has an aggressive program of leak detection and water service line replacement and will continue that. Plans are also being made for the pigging of water mains to remove biofilms from pipe walls. Discussions are on-going as to how to approach the cleaning of private property such as the pro-active replacement of water service lines and shock chlorination of interior plumbing systems after system-wide disinfection is established. Includes 20 references, tables, figures.