Effect of magnetic flux density on Escherichia coli, Salmonella species and chemical properties of River Njoro water

Abstract

The disinfection of water is of prime importance both for the animals and humans, since the presence of microorganisms in water may cause diseases including hepatitis, cholera, typhoid fever and dysentery. Reagents, techniques based on the use of a broad range of chemical agents are commonly used to disinfect water. Among them are chlorine, fluorine, ozone and ions of heavy metals. However, in the case where some organic substances remain in water, chlorine and ozone reacts with them forming carcinogenic substances. Moreover, many reagents are toxic and necessitate safety precautions in their transit and dosage. Some of them when applied result in variations in the composition and properties of water and adversely affect animal and plant life. For this reason, reagent techniques cannot fully meet modern requirements on the disinfection of water. The reagent less techniques are of great interest and may include physical methods based on the use of various physical fields for disinfection. Among them are ultraviolet rays, constant electric fields and magnetic fields. An important advantage of these physical techniques is their ability to act directly on microorganisms, leaving the properties and composition of water virtually intact. In this study experimental results of the disinfection process of water by means of magnetic fields are presented. Water samples were collected from River Njoro. Microbial count (Salmonella species and E. coli) for the samples were obtained using Membrane Filtration techniques. Spectrophotometry procedure was carried out to determine the concentration of Ca2+ and Mg2+ ions in the water. The pH value of the water was also taken using a pH meter. The samples were then exposed to different magnetic flux densities (2mT, 6mT and 10mT) at time intervals of 6 hours and 18 hours for each magnetic flux. Membrane filtration, Spectrophotometry and pH measurements were done before and after magnetic treatment of the samples. The data obtained was photographed and presented in tables and bar graphs. It was then subjected to One-way ANOVA, regression and correlation analyses. The means were separated using the Least Significant Difference. The maximum disinfection efficiency was 82.2% for E. coli and 77% for Salmonella species. It was also found that treatment with magnetic field did not alter the concentration of Ca2+ and Mg2+ ions as well as the pH values of River Njoro water. Magnetic treatment can possibly be used as a cost-effective method of disinfecting water for domestic consumption to reduce likely incidences of waterborne diseases.