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Critical Review and Analysis of the H2S Method for Detection of Fecal Contamination of Drinking WaterEPA Grant Number: F07D30734
Title: Critical Review and Analysis of the H2S Method for Detection of Fecal Contamination of Drinking Water
Investigators: McMahan, Lanakila
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Manty, Dale
Project Period: September 1, 2007 through September 1, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text | Recipients Lists
Research Category: Drinking Water , Academic Fellowships , Fellowship - Environmental Microbiology
The H2S method has been tested in many places in different waters and produced results indicating it to be a reasonable approach for testing treated and untreated waters for fecal contamination. It offers many advantages including low cost (estimated at 20% of the cost of coliform assays), simplicity, and ease of application to environmental samples. The test can be performed in settings where no laboratory facilities are available, minimally trained persons can do it and the results are easy to score as negative (no visual change in the water sample) or positive (appearance of a black color in the water sample due to iron sulfide precipitation). However, no systematic efforts have been made to determine directly if H2S tests fulfill the essential criteria for an indicator of fecal contamination in treated and untreated drinking water and its sources. This research would work to develop a simplified, quantitative, low-cost version of the H2S test for use in developed and developing countries.
This research will focus on the following: a) Evaluating the application of the H2S through an estimation of the concentration of H2S bacteria from the most probable number method using multiple dilutions and sample volumes; b) Using lab made and commercially-made H2S media for their performance in wastewater and fecally contaminated water; c) Comparing fecal contamination of water using optimized test versus E. coli test or enterococci tests when applied to samples of fecally contaminated water and wastewater; d) Determining whether or not the concentrations of H2S bacteria in water are predictive of risks of water-borne illness from fecally contaminated drinking or recreational waters in epidemiological studies; f) Developing test based on media from low-cost materials available world-wide including using cheap plastic bags instead of expensive plastic bottles.
This research should produce a simplified, quantitative, low-cost version of the H2S test that is used both in rural areas of the US and throughout the World to test water for microbial indicators and compare its effectiveness to other fecal coliform tests. Lastly, this test might be able to help determine whether or not the concentrations of H2S bacteria in water are predictive of risks of water-borne illness and can be used to make policy changes that reduce the mortality attributed to unsafe water supplies worldwide.