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The efficacy of silver/copper nanoparticles in biofilm control on water supply pipeline materials.

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Biofilms are microorganisms that inhabit inside a matrix made mainly of exopolysaccharides that are secreted from the micriobual consortia. Silver and copper ions efficacies have been proven in vitro, but, Huang, et al., (2008) confirmed the problem of biofilms altering the effects of these chemicals on the bacteria. The microbial killing effects of copper are in consequence of oxidation of the sulfhydryl groups of enzymes within the bacterial cell. The oxidation of these enzymes inhibits the enzymes activity halting the respiratory function of the cell, thus killing the bacterial cell (Pyle, et al., 1992). Silver nanoparticles increase the permeability of the cell membrane leading to cell leakage. The infiltration of silver ions in the mitochondria of the cell disrupts the ATP production by affecting the respiratory function enzymes resulting in the deformation of the chain that forms ATP. In a preceding study, biofilm bacterium were exposed to silver nanoparticles for various periods in 1mg and 2mg (per 25ml) concentrations. The results displayed a natural log delay with the required bacterial count being obtained at day 7. The research herein, was aimed at investigating the reduction of the effective time, the synergetic effects of copper nanoparticles and the application of nanoparticles in flow conditions. Concentrations of 10mg, 20mg and 50mg (per 25ml) of silver and copper nanoparticles were utilized in beaker and channel flow experimental setup varying the exposure time. A combination of copper and silver nanoparticles with concentrations 5mg ,10mg and 50mg were also tested in similar conditions to investigate the synergetic effects of the two heavy metals. In this experiment the silver nitrate and copper nitrate were reduced by citric acid and sodium hydroxide was used as the analytical agent. Given the results obtained, it is seen that the chemical application with flow aids the reduction of bacteria and the optimum concentration is between 10mg and 20mg (per 25ml) and it can be concluded that there is a synergetic effect between the silver and copper nanoparticles.


Masters Degree. University of KwaZulu-Natal, Durban.