Hydrogen Sulphide Test Strips and the Detection of Groundwater Contamination by Septic Seepage

The H2S test strip method is being advanced for microbiological water quality testing in situations where conventional analyses are impractical or too expensive. It involves ambient temperature incubation of water samples with nutrient test strips formulated to generate hydrogen sulphide when 'faecal ' bacteria are present. Recently a WHO review (Sobesey & Pfaender 2002) identified several concerns including the limited number of comparative studies, formulation variability, and false positives and negatives. In response to the WHO review we compared the H2S test's ability to detect and quantify faecal contamination in an aquifer impacted by septic leachfields with data obtained concurrently using conventional analytes- Escherichia coli, Enterococci, Clostridium perfringens, somatic and F-specific coliphages, faecal sterol biomarkers, Cryptosporidium and Giardia. Like other analytes, H2S testing detected the steep contamination gradient ranging from high (septic liquid) to moderate (exfiltration zones), to background (domestic bores), corresponding to indicator reductions/dilution>99.9999%. Single plus/minus tests were unable to distinguish between heavily and slightly contaminated waters. Multi-tube testing, especially using 10 X 10 mL arrays, however, allowed the pollutant gradient to be detected. It was concluded that while the WHO review concerns are justified, the H2S test performance shows promise in sanitary survey work and can be improved by employing a multiple tube / mpn approach and has potential for the protection of source water and identifying contamination