Productsin Contact with Drinking Water:
Investigationsinto the Metal Extraction and Microbiological Growth Tests
ReportNo WSAA 122
Thisproject, jointly funded by the Urban Water Research Association of Australiaand the South Australian Water Corporation, was undertaken for the purpose ofresolving issues relating to Australian Standard 4020 (Interim), “Products foruse in contact with water intended for human consumption with regard to theireffect on the quality of water” (Standards Australia, 1994a).
Theaims of the project were to assess modifications to practical test methods forproducts in contact with water in relation to Appendix G – the ability to leachheavy metals from the product into the water and Appendix D – the ability ofthe product to support the growth of microorganisms.
Theprincipal findings of the research are:
Forthe metals extraction test (based on the examination of seven copper orcopper/lead alloy products):-
· The test can be undertaken using extractant water with hardness up to100mg/L )as CaCO3) without influencing whether the products pass orfail AS4020 (Int). Based on this observation use of an extractant containing50mg/L hardness (as CaC O3) is suggested as more representative ofthe majority of reticulated supplies throughout Australia.
· Metal alloys containing 1.75% or greater lead failed to comply withAS4020 (Int) regardless of the hardness of the extractant water or temperatureof incubation (20° or 90°). Copper concentrations inthe extracts complied with the NH&MRC/ARMCANZ health guideline for drinkingwater. A new protocol using a test rig to simulate use of end of line taps isbeing investigated at the AWQC and a pooled extractant is used for analysis ofleached metals.
· Generally higher concentrations of copper and lead were extracted fromproducts at 90°C than for the 20°C incubation temperature.This has implications for the revision of AS4020 (Int) to include a hightemperature test for products used at elevated temperatures.
Forthe microbiological growth test (based on the examination of four products):-
· It was not possible to recommend an altered method of extraction orchange for the microbiological growth test based on the investigations owing tothe limited number of products that could be tested during the project.
· Although only a limited number of products were examined, results for P.aeruginosa and MDOD using extractantspecified in AS4020 (Int) would have produced a similar outcome for three ofthe four products tested (in relation to conforming with or failing to satisfyAS4020-Int.) The fourth (polyester/plasticised PVC) passed the P.aeruginosa test but failed the MDODtest. Both test methods gave similar outcomes when the synthetic extractionwater containing an increased concentration of bacterial nutrients was used.However some of the replicates produced variable results with both extractantwaters.
· Coliforms failed to grow in any extractant waters or the controls.Further research would be required to assess the reasons for non-growth of thecoliforms (possibly with development of a different nutritive extractant) andto investigate whether paraffin wax is a suitable control for coliforms inthese situations.
· Further research is required to test the suitability of the syntheticnutrient medium developed for the P.aeruginosagrowth test using a larger number of products.
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