Metals disinfection of E. coli in synthetic groundwater and effects of varying water chemistry

J.N. Edokpayi, R. Singh, J.O. Odiyo, J.A. Smith
University of Venda,
South Africa

Keywords: E. coli, diarrhea, disinfection, drinking water

Summary:

The sustainable access to clean and safe drinking water remains as global challenge as large numbers of people still consume water that is not safe. Diarrhea; a preventable waterborne disease remains the major cause of death among children under the age of 5 in most developing countries of the world. Several technologies have been invented to provide point of use water treatment devices. The cost of such materials often limits their application. This study seeks to evaluate the use of several metals below the World Health Organization recommended guideline values in drinking water as alternative metals in point of use water treatment devices. The bactericidal activity of Ag, Cu, Co, Ni and Zn against non-pathogenic strain of E. coli in synthetic ground water was evaluated. Different concentration of silver varying from 20, 40, 60 and 80 µg/l were tested for disinfection efficacy. Samples were taken at 2, 4, 6, 8, 18 and 24 h time points. Similarly, copper concentrations were varied from 200, 400, 600 and 800 µg/l. Samples were withdrawn at 4,6,8,12,18 and 24 h to count viable bacteria using IDEXX technique. Results showed that 80 µg/l of Ag gives 4log-8.5log reduction of E. coli between 2 to 24 h. While, 800 µg/l of Cu showed 1log-7log reduction of E. coli in the range of 4 to 24 h. A very high concentration (2800 µg/l ) of Zn showed 1log-5.2log reduction of E. coli between 24-72 h. Whereas, Co and Ni did not show any significant disinfection of E. coli even after 72 h. Change in the water chemistry slightly influenced the extent of disinfection. It is recommended that further work be carried out on technology involving copper because it is cheap and have a higher allowable concentration in drinking water when compared to silver.