dr. christiane schell
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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.deDVGW 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.deaerator (seen from the front and the back)
11Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
www.hyg.dewww.hyg.deDVGW W 270: GoalThe 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
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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
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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
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DVGW W 270: ScopeTest 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
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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
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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
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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
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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)
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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
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Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
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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 ?
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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
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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)
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positive control: paraffin
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negative control
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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)
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0,07
0,05
A B
A
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Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
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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
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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
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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
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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
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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)
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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]
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DVGW W 270: EvaluationSatisfactory 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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Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
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DVGW W 270: Evaluation
negative control
38Schell-Twinning 2009
Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin
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DVGW W 270: AssessmentFrom 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
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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)
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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
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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
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DVGW W 270: Report/Certificate• Test report
– Material / product descriptione.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)
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Against microbial surface biomass on cpdw
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