C 2009 Tuschewitzki Hygiene-Institut des Ruhrgebiets Institut für Umwelthygiene und Umweltmedizin 1 PD Dr. Georg-Joachim Tuschewitzki Enhancement

1C 2009 Tuschewitzki

Hygiene-Institut des RuhrgebietsInstitut für Umwelthygiene und Umweltmedizin

www.hyg.dewww.hyg.de

PD Dr. Georg-Joachim Tuschewitzki

Enhancement of Microbial Growth on Materials which come in Contact with Drinking Water – Testing and AssessmentTechnical Standard W 270 (November 2007)

Hygiene-Institut des Ruhrgebiets Institut für Umwelthygiene und Umweltmedizin




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


















www.hyg.dewww.hyg.deHoses used during repair of water pipe




























aerator (seen from the front and the back)




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




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




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




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




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




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




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)




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










positive control: paraffin







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 12 +- 5 °C




0,07

0,05

A B

A




0,1

0,20,3

0,5

Sediment

1,0

negative control positive control




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 20 +-2 liter/hour, 12 +-5 °C




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






www.hyg.dewww.hyg.deComposite materialsTube with two layers

How to test the inner layer without influence of the outer layer ?




Test module for pipes, tubes and hoses

only the surface in contact with drinking water is exposed and tested




Harvesting microbial growth biomass

conival stopper with the relevant diameter on a rod of stainless steel,

push through the tube




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





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)





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




negative control




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 < = (0,05 +- 0,02) ml /800 cm² comply with the requirements of this standard an can be used without restrictions from microbiological point of view





• 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 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





• 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




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




against microbial surface biomass on cpdw

• use certifiedcpdw

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C 2009 Tuschewitzki Hygiene-Institut des Ruhrgebiets Institut für Umwelthygiene und Umweltmedizin 1 PD Dr. Georg-Joachim Tuschewitzki Enhancement