Biofilms in copper plumbing systems: sensitivity to copper and chlorine and implications for corrosion

Microbial biofilms have been implicated as a major contributor to the corrosion of metals in drinking water distribution systems. This study investigated the sensitivity of biofilm bacteria with previously established cuprosolvency activity, isolated from domestic copper plumbing pipes, to chlorine and copper and assessed their potential to adsorb aqueous copper. Bacterial suspensions were exposed to free chlorine residuals of 0.1, 0.2 and 0.5 mg/L and viable bacteria enumerated at times 0, 1, 2, 5 and 10 minutes. Disinfection curves showed the isolated bacteria were more resistant to free chlorine in comparison to the indicator organism Escherichia coli. Disc diffusion assays demonstrated high resistance by all bacteria to copper, with a Corynebacteria sp. showing no growth inhibition at concentrations up to 4 gCu/L. The isolated bacteria showed the ability to bind aqueous copper ions from solution in adsorption experiments. Significantly higher adsorption of copper was shown by a species of Pseudomonas. The results of this research will provide a greater understanding of causes of biofilm accumulation and copper contamination of drinking water, aiding in health risk assessment and risk management.