AWWA WQTC69323

This powerpoint presentation begins by providing a brief overview of internal metallic pipe corrosion encountered in water distribution systems, factors impacting corrosion, and water treatment plants (WTPs) of the City of Marco Island. Study objectives and approach included the following: investigate the causes of copper pitting; review water quality and process chemistry to determine if correlations exist between water quality, plant operations, and process control changes; conduct interviews with consumers based on complaint records; and, provide recommendations on necessary actions required to control copper pitting. Research findings indicate the following: the majority of the pitting problems occur in horizontal cold water copper piping; many of the cases reported in the City's plumbing system are due to the Type M copper; there is sufficient evidence that Type L copper is much more durable and compatible with the City's water quality; no conclusive evidence was found that electrical grounding is an issue in the copper pitting corrosion in the City's residential piping; a potential cause of pitting is a biological attack on the copper piping caused by the growth of nitrifying bacteria in the distribution system; and, the low alkaline water in the distribution system tends to be slightly under-saturated for calcium carbonate based on the Langelier Saturation Index. Includes table, figure.