Characterization of Ionic Copper for Disinfection of Stored Drinking Water

Drinking water remains highly vulnerable to contamination during collection, transport and storage when it is not subjected to chemical treatment that provides a disinfectant residual. In areas where piped water quality is unreliable and service is intermittent, even treated water is susceptible to recontamination. There is a need for a low-cost and effective alternative to current methods of water storage that provides an adequate disinfection barrier against recontamination. Better understanding of the antimicrobial activity of certain metals in their ionic form is needed for the use of such metals to be considered protective as a safe storage disinfection practice. The efficacy of copper ions to inactivate the microorganisms Escherichia coli B, Pseudomonas aeruginosa, and MS-2 coliphage was tested as a first phase in this research. Batch disinfection reactions were conducted in reagent grade test waters maintained at 18°C and buffered at pH 7.2. Ionic solutions of copper chloride ([dissCu]=01, 03, 1, and 3mg/L) were dosed to batch reactors seeded with all three microorganisms. Samples were assayed at 0, 0.3, 1, 3 and 6 hours. The disinfection results from replicate experiments were normalized and averaged in order to generate semi-log inactivation curves for each copper dose. Greater than 2 log(20) reductions of bacteria and viruses were observed after 6 hours with [dissCu]doses > 0.3 mg/L, well below the 2 mg/L WHO guideline value for copper in drinking water. Maximum reductions of E. coli B and P. aeruginosa occurred after 6 hours with a dose of 3 mg/L [dissCu] and were 8.5 log(10) and 36 log(10), respectively. The maximum reduction of MS-2 coliphage occurred after 6 hours with a dose of 1 mg/L [dissCu] and was 2.4 log(10). Both bacterial reactions appeared to follow exponential kinetics. The Chick-Watson model was able to provide best estimates of rate constants for inactivation of E. coli B, P. aeruginosa, and MS-2 with [dissCu] which were 0.045±0.009, 0.010±0.004, and 0.018±0.005, L/mg x min, respectively. Comparisons of Ct values and in activation rate constants indicate that [dissCu] is able to maintain the microbiological quality of drinking water as well as combined chlorine. This work demonstrates that ionic copper deserves further consideration as an alternative method of protecting drinking water from microbiological contamination during collection, transport and storage.Master of Science in Environmental Engineerin