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Georgia Journal of Science

Article Title

THE ABILITY OF WATER TREATMENT RESIDUALS TO FILTER RHODAMINE-COATED MICROPARTICLES AS PATHOGEN PROXIES AT DIFFERENT IONIC STRENGTH AND PH LEVELS

Abstract

Contamination of water by pathogens such as bacteria, viruses, and protozoa is a worldwide problem and the most common source of these contaminants is point sources from cattle enterprises. Water treatment residuals (WTRs), a byproduct of surface water treatment for drinking, were studied for their ability to filter contaminants through column flow experiments. WTRs are good candidates for filtration devices due to their high clay content, and resulting high numbers of sorption sites. The WTR used in this study are composed primarily of kaolinite clay. Quartz sand is widely used as a filtration medium, and was used as a control in this study. Sand and WTRs were filtered at size-60 mesh to remove fine particles. Rhodamine-coated microparticles (RMPs) were sent through column flow experiments as proxies for pathogens such as large bacteria such as Salmonella enterica and small protozoa such as Cryptosporidium because they are of similar size, and can be easily measured with through fluorimetry. WTRs filter RMPs primarily through sorption and/or straining. Column flow experiments are being run to test WTR filtering ability under varying solution chemistry at two different pH levels (5 and 7.6) and two different ionic strengths (3 mM and 15 mM) representative of environmental conditions found in Georgia. The pH and ionic strength changes alter the surface charge environment and potentially sorption of RMPs onto WTRs and quartz sand. A conservative chlorine tracer was used for comparison. Preliminary data shows WTRs had a small retardant effect on the RMP compared to the normal flow of water through the column, but also had created preferential flow and moved RMPs through the column more quickly. The different combinations of pH and ionic strength have not yet appeared to have any significant difference on the retardation of the RMP.

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