Tests for coliform bacteria and Escherichia Coli (E.Coli) by the membrane filter technique (see ISO 9308-1) are the most important routine microbiological examinations carried out on drinking water. These tests are based on membrane filtration by vacuum, subsequent culturing on a differential agar medium and calculation of the number of target organisms in the sample.


Advantages of the nutrient pads using the filter method


  • Nutrient pads are sterile, dehydrated culture media. Once they are moistened with sterile and demineralized (or distilled) water, they are ready to use immediately
  • Eliminates handling errors in the preparation of culture media
  • Dehydrated nutrient pads eliminates time-consuming and laborintensive preparation of culture media
  • Conforms to ISO 9303-1, ISO 7899, ISO 6222 and others
  • The visible colonies can be related directly to the sample volume. They give quantitative results. Compared with the direct method, considerably larger sample volumes can be tested. This concentration effect increases the accuracy of microbiological detection
  • Adequate for the determination of E. coli and coliforms, Enterobacteria, Salmonellae, wild yeasts, yeast and mold, etc. utilizing the different nutrient pad types
  • Typical application examples are not only the detection of microorganisms in the water, but also in beer, foods, milk, pharmaceuticals, soft drinks and wine
  • The incubated membrane filters are easy to file as a permanent record for convenient traceability
  • Sartorius Membrane Filters are manufactured unter GMP conditions ensuring consistent quality and high reproducibility from batch to batch and within each batch


Membrane filter method with nutrient pad sets


  1. Label the needed amount of Petri dishes
  2. Wet the pads with 3 -3.5 ml of water
  3. Open the stopcock, flame the filter support
  4. Flame the funnel. Then place it on the filter support
  5. Open the vacuum valve and flame the inside of the funnel
  6. Flame the forceps
  7. Open the cover of the sterile filter. Take it out with the sterilized forceps
  8. Place the filter disc on the filter support
  9. Remove and discard the yellow protective disc
  10. Place the funnel on the funnel support and close the clamp
  11. Open the valve and filter the sample, rinse with water. Close the valve again
  12. Remove the funnel and take the filter disc
  13. Place the filter disc on the Nutrient Pad Set
  14. Place the Petri dish with lid above into the incubator

See TRAWAS in action


Billwerder Ring 10, 21035 Hamburg, Germany
Tel.:  +49 (40) 734741-0, Fax: +49 (40) 734741-10