The method describes the qualitative determination of sulphite-reducing, spore-forming anaerobes in mineral, spring and table water using single-strength dextrose-iron sulphate-sodium sulphite agar (DRCM agar) (according to Annex 2, point 4a to § 4 para. 3 of the German Mineral and Table Water Ordinance of 1 August 1984, as amended on 5 July 2017).
Mineral, spring and table waters as well as drinking waters that are to be marketed.
Qualitative detection of sulphite-reducing, spore-forming anaerobes in mineral water, spring water, table water, and other drinking water bottled for distribution to the consumer, by means of membrane filtration and placing the filter on a solid culture medium.
Note 1: If only the spores of sulphite-reducing anaerobes are to be analysed, the prescribed sample volume must be heated at 75 °C ± 1 °C for 10 minutes in order to inactivate the vegetative cells. Then cool quickly with cold water.
Important: Carry out a comparative test with the same volume of tap water to determine the total heating time required in the water bath.
Membrane filtration (MF) and placing the filter on dextrose-iron sulphate-sodium sulphite agar (DRCM agar) (corresponds to method Annex 2, point 4 a of § 4 para. 3 of the German Mineral and Table Water Ordinance, MTV) [1].