Copper is the most widely used metal for household plumbing systems. The Lead and Copper Rule or LCR, sets the action level for copper in the distribution system as 1.3 mg/L. Copper corrosion can cause not only health effects but also damages the water supply infrastructure. A portion of the corrosion of copper is influenced by microbial activities. It is also known that water quality factors having the greatest affect on lead and copper corrosion are pH, alkalinity or dissolved inorganic carbonate (DIC), orthophosphate concentration, and buffer intensity. Also, as the microbial community in the distribution system is influenced by nutrients, the nutrient concentration in water may play a significant role in microbial copper corrosion. Because of the DBP Rule many water utilities have switched to monochloramine. When monochloramine decays it forms ammonia, which may influence copper corrosion and cause nitrification in the distribution system and plumbing systems. The objective of this project is to investigate the effect of total organic carbon and ammonia on copper corrosion under stagnant flow conditions and to discover the diversity of the biofilm in a simulated plumbing system. A modified version of the commonly used CDC reactors developed at the Center for Biofilm Engineering was used in this project. In the first set of experiments two types of copper coupons (new and old, I.e. pre-exposed to 0.1N NaOH solution) were used. These reactors were fed with water with different carbon (2～4ppm) and ammonia (0.36～0.71ppm) concentrations and biologically treated tap water to supply the bacterial population. Water in the reactor was stagnant for eight hours and then flowed for five minutes. Copper corrosion increased with an increase of organic carbon content. Heterotrophic plate counts also showed higher numbers for high carbon reactors. This experiment was conducted for three months but did not show any sign of nitrification. In the second set of experiments, pre aged copper and PVC coupons were used with high carbon (4 ppm) and ammonia (0.36 and 0.71 ppm) feed. After three months of operation, the PVC reactors showed evidence of nitrification, while the copper reactors also expressed nitrification within five months. This difference in onset may be due to the toxicity of the copper to microbial growth. The microbial population in those reactors was analyzed using PCR and DGGE.
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