Student Research: Laura McLaughlin
Chlorine can be an effective disinfectant for centralized water treatment systems, and has been recommended by the CDC as point-of-use (POU) drinking water treatment option. However, POU chlorination may not adequately treat drinking water in rural settings due to dependency on a variety of human factors, such as household contamination and ease-of-use, as well as uncontrolled water-quality variables, such as turbidity or inorganic and organic materials in water. In this study, the effectiveness of POU chlorine disinfection in rural Ecuador was measured with and without chlorine use. The laboratory component of this study was designed to evaluate the effects of human and water quality variables on chlorine disinfection. In both settings, indicator organisms of fecal contamination were measured before and after chlorine addition. Analysis of household data using Wilcoxon Rank Sum Hypothesis Test showed statistically insignificant differences in log removals between chlorine and non-chlorine households, p-values were 0.08, 0.10, and 0.16 for E. Coli, Enterococci, and some somatic coliphage, respectively. In contrast, the log reductions of indicator organisms between chlorine-treated samples and non-chlorine treated controls in the laboratory were significantly different, p-values were 0.04, 0.02, and 0.02 for E. coli, Enterococci, and some somatic coliphage, respectively. These data show that chlorine is significantly more effective in the lab than in the field.
UV-disinfection is commonly used in municipal wastewater systems, and has also been proposed as a promising POU alternative to chlorine. Also in this study, the MEDRIX UV disinfection system, was evaluated in a laboratory setting. All UV laboratory experiments used water seeded with known lab culture concentrations of coliphage, E. coli and Enterococci. Samples were taken from the flow-through UV system at the inlet and outlet to calculate log reductions. In phosphate buffered water, median log removals were 5.1, 5.5, and 4.1 for E. coli, Enterococci, and coliphage. In turbid water, removals were 4.8, 4.8, and 3.6 for E. coli, Enterococci, and phage. In water with 2 mg/l iron, removals were 4.9, 5.3, and 2.0 for E. coli, Enterococci, and phage. This study suggests UV has a laboratory effect similar to chlorine in water without high iron concentration.