PD Dr. Georg-Joachim Tuschewitzki

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

2 DVGW W 270: Motivation What`s the motivation? Noticable problems,
Poor quality of the 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

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8 Hoses used during repair of water pipe

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17 aerator (seen from the front and the back)

18 DVGW W 270: Goal The goal To exclude microbial impact on drinking water, only materials without microbial growth enhancement (by contact with drinking water) may be used Identify materials without formation of significant microbial growth (slime) drinking water is not sterile, so some microorganisms may develop on the surface of material in contact with drinking water; this limited development cannot be avoided and is therefore tolerated (first steps of biofilm, colonisation) But: no tolerance for a stimulation and promotion of microbial growth by substances coming from the construction product and the development of surface biomass

19 DVGW W 270: Goal 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 the drinking water Surface biomass can become a potential habitat for pathogens

20 DVGW W 270: scope Test method to determine microbial growth on
organic materials materials containing organic components forseen to get into contact with drinking water or with water to become drinking water

21 DVGW W 270: scope Test method applies to materials
already finished (factory made) 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 not containing organics

22 DVGW W 270: principle Test objects are
cleaned with disinfectant rinsed with drinking water Exposed to slow flowing test water Test container Defined periods of times removed from the water surface growth biomass is harvested by scraping centrifugation determination of biovolume

23 DVGW W 270: basic requirements
Test objects shall be representative Composition Treatment Properties to finished products composite products shall be tested as product material composition shall comply with national regulations, be approved by the test laboratory

24 DVGW W 270: reference materials
to insure that the test runs are undisturbed Positive control: development of biomass (paraffin) Negative control: only surface colonisation but no biomass development (stainless steel)

25 DVGW W 270: apparatus and reagents
Test container Glass, stainless steel, (inert material) Volume approximately 100 liter Water inflow at the bottom, outflow on top of the container at the other side Scraper Rubber lid or hard plastic (12-15 cm) Centrifuge Swing out rotor, 3000 x g acceleration of gravity

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28 positive control: paraffin

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30 DVGW W 270: apparatus and reagents
Glassware for centrifugation Type A: Specially formed calibrated 0,01-0,4 ml Type B: for volumes of surface biomass expected to be more than 0,5 ml (positive control), conical centrifugation tubes with a volume up to 15 ml are recommended Test water Without disinfectants Temperature °C

31 A A B 0,07 0,05

32 0,5 0,3 0,2 0,1 1,0 Sediment negative control positive control

33 General In each test container
DVGW W 270: test procedure General In each test container one positive and one negative control different test objects Total contact with flowing water at all sides No contact with other test objects or control Darkness Permanent flow liter/hour, °C

34 Removal of test objects
DVGW W 270: test procedure Removal of test objects Let the water drip from the test objects (1 +-0,5 min) Biomass: removed by a scraper and completely transferred to the glassware for centrifugation Contact cultures from samples without surface growth biomass Re-exposition of test pieces, after harvesting and cleaning under flushing water Centrifugation (10 min 3000 x g or 5 min 4000 x g) Determination of biovolume Examination of surface growth biomass

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36 Composite materials Tube with two layers
How to test the inner layer without influence of the outer layer ?

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

38 Harvesting microbial growth biomass
conival stopper with the relevant diameter on a rod of stainless steel, push through the tube

39 1-monthly (2 test pieces, each 800 cm²)
DVGW W 270: Test Periods 1-monthly (2 test pieces, each 800 cm²) exposed for 4 weeks, examined: result 1a exposed again for 4 weeks, examined: result 1b exposed again for 4 weeks, examined: result 1c 2-monthly (2 test pieces, each 800 cm²) exposed for 8 weeks, examined: result 2a 3-monthly (2 test pieces, each 800 cm²) exposed for 12 weeks, examined: result 3a

40 if results are uncertain: 2 additional test periods optional
DVGW W 270: Test Periods if results are uncertain: 2 additional test periods optional 1-monthly (2 test pieces, each 800 cm²) 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 800 cm²) exposed for 8 weeks, examined: result 2a exposed for 8 weeks, examined: result 2b (optional) 3-monthly (2 test pieces, each 800 cm²) exposed for 12 weeks, examined: result 3a

41 satisfactory test performance
DVGW W 270: Evaluation satisfactory test performance positive control: microbial surface biomass >= 1,5 ml / 800 cm² negative control: no microbial 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

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43 DVGW W 270: Assessment From the parallel results (2 test pieces: 2 x 800 cm²) the arithmetic mean is calculated A) Materials which have over all test periods solely a surface colonisation or a microbial surface biomass < = (0, ,02) ml /800 cm² comply with the requirements of this standard an can be used without restrictions from microbiological point of view

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

45 DVGW W 270: Assessment D) materials used for joints (category D2 the limit values are (0,20+-0,03) ml/800 cm². Exception: first 1-monthly-test period. Additionaly: values shall be equal or show a decreasing tendency 1c <= 1b, 3a <= 2a E) materials showing neither surface growth biomass nor surface colonisation do not comply with the requirements of this standard with regard to be used in contact with drinking water

46 DVGW W 270: Report, certificate
Test report Material, product description Manufacturer, compositional information (presented, evaluated and approved), method of production, range of use Test sample, results, additional findings, assessment Test certificate …. assessment, validity, remark: valid only without changes

47 against microbial surface biomass on cpdw
use certified cpdw gasket