Q-262. Evaluation of a Quantitative Test for Hydrogen Sulfide Producing Bacteria to Predict Drinking Water Quality

L. McMahan, C. E. Stauber, M. D. Sobsey;
Univ. of North Carolina, Chapel Hill, NC.

The H2S method has been tested in various water sources throughout the world and has produced results indicating it is a reasonable approach for testing both treated and untreated waters for the presence of fecal contamination. It offers many advantages, including low cost, simplicity, and ease of application to environmental samples. The purpose of this research was to develop a quantitative, low-cost version of the H2S test for use in developed and developing countries by evaluating: a) the application of a most probably number (MPN) method H2S test through an estimation of H2S-producing bacteria concentration using multiple dilutions and sample volumes; b) the performance of lab-made (both autoclaved and tyndalized broth) and commercially available H2S media; c) incubation at ambient (25 C) and conventional (37C) temperatures and d) the substitution of low-cost plastic bags for expensive plastic or glass bottles. One-Way ANOVA showed no significant difference between the mean MPN values for the commercially available medium and both lab-made H2S broths, when compared at 25 and 37C and at 24 and 48 hours of incubation. There was also no significant difference between the mean MPN values for the same medium incubated for 24 and 48 hours. Performance of different H2S methods was not significantly different in 2-way comparisons for either 24 or 48 hours of incubation considered separately. There was also no significant difference in H2S test performance between bags and bottles compared separately at 24 and 48 hours of incubation. We conclude that lab-made H2S media can be employed when commercial media is either unavailable or cost-prohibitive. Moreover, inexpensive plastic bags are as effective in the test as more expensive plastic or glass bottles. Overall, our results on modified H2S test methods suggest that as the development of a single step, plastic bag, MPN method is feasible is for successful application in resource-limited settings.