MIKROSVAMP OCH AKTINOMYCETER I DRICKSVATTEN / Microfungi and actinomycetes in drinking water

During the last two decades analyses of microfungi (yeasts and moulds) and actinomycetes have been conducted on drinking water in Sweden. From originally being a pilot study conducted to obtain knowledge of the extent to which these microorganisms can be detected in untreated water and in the distribution network, today the analyses are conducted both in control programmes and to investigate complaints concerning odour and taste, as well as skin irritation. The studies show that there may be conditions for growth of mould and actinomycetes in a distribution network that will have an effect on the quality of the drinking water. High concentrations of organic material in the water favour growth of microorganisms. Reservoirs, tail pipes, filters and filter material are places in a distribution network where enrichment and growth of both fungi and actinomycetes can take place. Further it has been shown that material from which pipes, reservoirs, pressure ranks, etc. are made can promote growth. The Drinking Water Directive contains rules for supervision, sampling and assessment (23). Experiences of the studies conducted illustrate the importance of control programmes with sampling points distributed throughout the entire network, also including the raw water. The limit values stated in the directive are based on quantitative analyses. In the future it will be justified also to conduct qualitative assessments by identifying mould fungi to genus or species. There are suspicions that, for example, species within the Phialophora genus, that are frequently found in drinking water, can cause skin irritation since they often dominate in drinking water and in high concentrations. More research is needed to establish the relationship between fungi and health effects. As regards actinomycetes, further knowledge is needed on which species can be demonstrated in drinking water, what effect they have on water quality, as well as their effects on health.