Products in Contact with Drinking Water: Investigations into the Metal Extraction and Microbiological Growth Tests
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No UWRAA 122
This project, jointly funded by the Urban Water Research Association of Australia and the South Australian Water Corporation, was undertaken for the purpose of resolving issues relating to Australian Standard 4020 (Interim), “Products for use in contact with water intended for human consumption with regard to their effect on the quality of water” (Standards Australia, 1994a).
The aims of the project were to assess modifications to practical test methods for products in contact with water in relation to Appendix G – the ability to leach heavy metals from the product into the water and Appendix D – the ability of the product to support the growth of microorganisms.
The principal findings of the research are:
For the metals extraction test (based on the examination of seven copper or copper/lead alloy products):-
- The test can be undertaken using extractant water with hardness up to100mg/L (as CaCO3) without influencing whether the products pass or fail AS4020 (Int). Based on this observation use of an extractant containing50mg/L hardness (as CaC O3) is suggested as more representative of the majority of reticulated supplies throughout Australia.
- Metal alloys containing 1.75% or greater lead failed to comply with AS4020 (Int) regardless of the hardness of the extractant water or temperature of incubation (20° or 90°). Copper concentrations in the extracts complied with the NH&MRC/ARMCANZ health guideline for drinking water. A new protocol using a test rig to simulate use of end of line taps is being investigated at the AWQC and a pooled extractant is used for analysis of leached metals.
- Generally higher concentrations of copper and lead were extracted from products at 90°C than for the 20°C incubation temperature. This has implications for the revision of AS4020 (Int) to include a high temperature test for products used at elevated temperatures.
For the microbiological growth test (based on the examination of four products):-
- It was not possible to recommend an altered method of extraction or change for the microbiological growth test based on the investigations owing to the 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 extractant specified in AS4020 (Int) would have produced a similar outcome for three of the 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 MDOD test. Both test methods gave similar outcomes when the synthetic extraction water containing an increased concentration of bacterial nutrients was used. However some of the replicates produced variable results with both extractant waters.
- Coliforms failed to grow in any extractant waters or the controls. Further research would be required to assess the reasons for non-growth of the coliforms (possibly with development of a different nutritive extractant) and to investigate whether paraffin wax is a suitable control for coliforms in these situations.
- Further research is required to test the suitability of the synthetic nutrient medium developed for the P. aeruginosa growth test using a larger number of products.