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Dr. Christiane Schell

Enhancement of Microbial Growth on Materials which come into Contact with Drinking Water – Testing and Assessment DVGW Technical Standard W 270 (November 2007). Dr. Christiane Schell. Hygiene-Institut des Ruhrgebiets Institut für Umwelthygiene und Umweltmedizin. DVGW W 270: Motivation.

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Dr. Christiane Schell

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  1. Enhancement of Microbial Growth on Materials which come into Contact with Drinking Water –Testing and Assessment DVGW Technical Standard W 270(November 2007) Dr. Christiane Schell Hygiene-Institut des Ruhrgebiets Institut für Umwelthygiene und Umweltmedizin

  2. DVGW W 270: Motivation • What was the reason? • Noticable problems, • Poor quality of drinking water and • Damages caused by microbial growth of slimy, slicky consistency lead to the development of an easy and simple test method orientated at practical needs [Method developed by Prof. Dr. med. Schoenen, Hygiene-Institut, Universität Bonn (Director Prof. E. Thofern),1984]

  3. aerator (seen from the front and the back)

  4. DVGW W 270: Goal • The goal • To exclude microbial impact on drinking water by materials which enhance microbial growth (by contact with drinking water) • To identify materials without microbial growth promoting properties (biofilm) • drinking water is not sterile, microorganisms may be present on the surface of materials in contact with drinking water; this limited development cannot be avoided and is therefore tolerated („natural“ colonisation) • But: no tolerance for stimulation and promotion of microbial growth by compounds being released from the construction product andleading to the development of surface biomass

  5. Limited colonisation can be accepted because the quality of drinking water will not be affected Surface biomass developement can not be accepted as the the quality of drinking water may be affected: Surface biomass can affect the colony count numbers of drinking water Surface biomass can become a potential habitat for pathogenic microorganisms DVGW W 270: Goal

  6. Test method to determine microbial growth on organic materials materials containing organic components foreseen to get into contact with drinking water or with water to become drinking water DVGW W 270: Scope

  7. Test method applies to materials already finished (factory made products) and site applied products (coatings etc.) The method is not applicable to greases and oils because of technical difficulties concerning the test procedure Testing is not necessary for materials containing no organics DVGW W 270: Scope

  8. Test pieces are washed in drinking water cleaned with disinfectant rinsed with drinking water exposed to slowly flowing test water defined test container defined periods of times removed from the water Surface biomass is harvested by scraping centrifugation determination of biovolume DVGW W 270: Principle

  9. Test samples shall be representativeto finished products Composition Treatment Properties Composite products shall be tested as product Material composition shall comply with national regulations, be approved by the test laboratory DVGW W 270: Basic requirements

  10. Reference materials to insure that the test runs are undisturbed Positive control: development of biomass by deliverance of biodegradable substances (paraffin) Negative control: only surface colonisation but no biomass development (e.g. stainless steel) DVGW W 270:Basic requirements

  11. Test water Without disinfectants Temperature 12  5 °C Test container Glass, stainless steel (inert material) Volume approximately 100 liter Water inflow at the bottom, outflow on top of the container at the opposite side DVGW W 270: Apparatus and reagents

  12. Test water Without disinfectants Temperature 12  5 °C Test container Glass, stainless steel (inert material) Volume approximately 100 liter Water inflow at the bottom, outflow on top of the container at the opposite side Test module for pipes and hoses DVGW W 270: Apparatus and reagents

  13. Composite materialsTube with two layers How to test the inner layer without interfering effects of the outer layer ?

  14. Test module for pipes, tubes and hoses only the surface in contact with drinking water is exposed and tested

  15. Test water Without disinfectants Temperature 12  5 °C Test container Glass, stainless steel (inert material) Volume approximately 100 liter Water inflow at the bottom, outflow on top of the container at the opposite side Test module for pipes and hoses Scraper With rubber lid or made of hard plastic (breadth 12 - 15 cm) DVGW W 270: Apparatus and reagents

  16. positive control: paraffin

  17. negative control

  18. Glassware for centrifugation Type A: Specially designed calibrated scale 0.01 - 0.4 ml Type B: conical centrifugation tubes with a volume up to 15 ml are recommended for volumes of surface biomass expected to be more than 0.5 ml (e.g. positive control) DVGW W 270: Apparatus and reagents

  19. B A A 0,07 0,05

  20. Glassware for centrifugation Type A: Specially designed calibrated scale 0.01 - 0.4 ml Type B: conical centrifugation tubes with a volume up to 15 ml are recommended for volumes of surface biomass expected to be more than 0.5 ml (e.g. positive control) Centrifuge Swing out rotor, 3000 x g acceleration of gravity DVGW W 270: Apparatus and reagents

  21. General In each test container one positive and one negative control different test pieces Total contact with flowing water at all sides No contact with other test pieces or controls Darkness Permanent flow of 20  2 liter/hour, 12  5 °C DVGW W 270: Test procedure

  22. Removal of the test pieces one by one from the container Removal of surface biomass by a scraper / stopper and complete transfer to the glassware for centrifugation DVGW W 270: Test procedure

  23. DVGW W 270: Test procedure Harvesting microbial growth biomass – tubes and hoses stopper with the relevant inner diameter on a rod of stainless steel, pushed through the tube

  24. Removal of the test pieces one by one from the container Removal of surface biomass by a scraper / stopper and complete transfer to the glassware for centrifugation Contact cultures from samples without surface growth Re-exposition of test pieces if necessary after harvesting and cleaning under flushing water Centrifugation (10 min 3000 x g or 5 min 4000 x g) Determination of biovolume Further examination of biovolume if necessary(e.g microscopy) DVGW W 270: Test procedure

  25. 1-monthly(2 test pieces, each of 800 cm² total surface) exposed for 4 weeks, examined: result 1a exposed again for 4 weeks, examined: result 1b exposed again for 4 weeks, examined: result 1c exposed again for 4 weeks, examined: result 1d [optional] 2-monthly(2 test pieces, each of 800 cm² total surface) exposed for 8 weeks, examined: result 2a exposed again for 8 weeks, examined: result 2b [optional] 3-monthly(2 test pieces, each of 800 cm² total surface) exposed for 12 weeks, examined: result 3a [optional expositions only under certain circumstances for materials used for joints and gaskets – D1 and D2] DVGW W 270: Test Periods

  26. Satisfactory test performance positive control: microbial surface biomass 1.5 ml / 800 cm² negative control: nomicrobial surface biomass < 0.01 ml / 800 cm², but positive contact cultures (microbial surface colonisation) If there is no satisfactory test performance the whole test run has to be repeated DVGW W 270: Evaluation

  27. DVGW W 270: Evaluation negative control

  28. From the parallel results (2 test pieces: 2 x 800 cm²) of each test period the arithmetic mean is calculated A) Materials which show over all test periods only surface colonisation or a microbial surface biomass  (0.05  0.02) ml / 800 cm² comply with the requirements of the standard and can be used without restrictions from microbio-logical point of view DVGW W 270: Assessment

  29. B)Materials which show at one test period a result of microbial surface biomass > (0,05  0,02) ml / 800 cm² do not comply with the requirements of the standard for general use in the range of drinking water C)Materials used for larger joints and gaskets (category D1):the limit values are (0,12  0,03) ml / 800 cm² Exception: first 1-monthly test period Additionally: values shall show equal or decreasing tendency (1c  1b, 3a  2a) DVGW W 270: Assessment

  30. D)Materials used for smaller joints and gaskets (category D2):the limit values are (0.20  0.03) ml / 800 cm² Exception: first 1-monthly test period Additionally: values shall show equal or decreasing tendency (1c  1b, 3a  2a) E)Materials showing neither surface growth nor surface colonisation do not comply with the requirements of the standard with regard to be used in contact with drinking water DVGW W 270:Assessment

  31. DVGW W 270: Assessment

  32. Test report Material / product description e.g. manufacturer, compositional information (presented, evaluated and approved), method of production (presented), range of use Details to test sample / pieces Test results, additional findings, assessment Test certificate …. assessment, validity (remark: valid only without changes in chemical composition) DVGW W 270: Report/Certificate

  33. Usecertifiedcpdw ! Against microbial surface biomass on cpdw gasket

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