Evaluation of the H2S method for detection of faecal contamination of drinking-water
Rolling revision of the WHO Guidelines for Drinking-water Quality
Evaluation of the H2S method is included in the plan of work of the rolling revision of the WHO Guidelines for Drinking-water Quality.
WHO receives many requests for information and comment on this microbiological test (e.g., from WPRO). It is a potentially important issue, particularly for developing countries. The purpose of the supporting document Evaluation of the H2S Method for Detection of Faecal Contamination of Drinking-water is to review the basis of the hydrogen sulfide test as a measure of faecal contamination of drinking-water and the available scientific and empirical evidence for and against the test as a valid, useful and reliable measure of faecal contamination and drinking-water quality. The draft report addresses the fundamental microbiological considerations of the test, including its chemical and biochemical basis, what organisms it detects, and how it detects and quantifies them and the reported experiences with its practical application to assessing water quality. A potential problem is that the test is non-specific and may provide false positives for sulfide in some waters that are not suffering sanitary contamination, but rather contain reducible sulfate. That would limit its use.
Revised draft report for review in early 2006; stand-alone supporting document for publication post-2006
Progress to date
The joint Microbial Aspects and Protection and Control Working Group meeting in Adelaide (2001) supported the view that a critical review of the significance and applicability of the H2S test should be added to the work programme of the Microbial Aspects Working Group and appointed a project coordinator. A draft working document on the use of the H2S test was presented and discussed in detail at the expert consultation in Loughborough (2001), and the meeting recommended that the document be peer reviewed once suggested changes had been addressed. The document has been peer reviewed, and some revisions have been made. One general comment was that the draft was ambiguous as to the value of the test and its utility as a screening tool. The draft document on the use of the H2S test will be finalized in fall 2005.