1Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
Dr. Christiane Schell
Enhancement of Microbial Growth on Materials which come into Contact with Drinking Water – Testing and AssessmentDVGW Technical Standard W 270 (November 2007)
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
2Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
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]
3Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
4Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
5Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
6Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
7Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
8Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
9Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
10Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
aerator (seen from the front and the back)
11Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
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 and leading to the development of surface biomass
12Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
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 drinking water
– Surface biomass can become a potential habitat for pathogenic microorganisms
13Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
14Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
15Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Scope
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
16Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Scope
• 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
17Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Principle• 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
18Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Basic requirements
• Test samples shall be representative to 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
19Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Basic requirements
• 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)
20Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Apparatus and reagents
• 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
21Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
22Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Apparatus and reagents
• 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
23Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.deComposite materialsTube with two layers
How to test the inner layer without interfering effects of the outer layer ?
24Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
Test module for pipes, tubes and hoses
only the surface in contact with drinking water is exposed and tested
25Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Apparatus and reagents
• 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)
26Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
positive control: paraffin
27Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
negative control
28Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Apparatus and reagents
• 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)
29Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
0,07
0,05
A B
A
30Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Apparatus and reagents
• 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
31Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Test procedure
• 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
32Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Test procedure
• 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
33Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Test procedure
stopper with the relevant inner diameter on a rod of stainless steel, pushed through the tube
Harvesting microbial growth biomass – tubes and hoses
34Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Test procedure
• 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)
35Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Test Periods 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]
36Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
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
37Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Evaluation
negative control
38Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Assessment
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
39Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Assessment• 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)
40Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Assessment
• 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
41Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Assessmentafter
4 weeksafter
8 weeksafter
12 weeksoptional:
after16 weeks
1-monthlytest periods
harvest of sur-face biomass(mean =result 1a)
harvest of sur-face biomass(mean =result 1b)
harvest of sur-face biomass(mean =result 1c)
harvest of sur-face biomass(mean =result 1d)
2-monthlytest periods
harvest of sur-face biomass(mean =result 2a)
harvest of sur-face biomass(mean =result 2b)
3-monthlytest periods
harvest of sur-face biomass(mean =result 3a)
42Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
DVGW W 270: Report/Certificate
• 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)
43Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.de
Against microbial surface biomass on cpdw
Usecertifiedcpdw !
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