water quality regime trialled in chis study produced better quality water based on the customers perception of caste and odour. T he results show that it is possible to successfully engage a commun ity to assess complex issues such as taste and odour with minimal specialist training. No attempt was made to standardise the numerical ratings of the participants. T herefore the individual numbers recorded by the participants reAect different sensitivities to the caste and odours of the water and also different expectatio ns fo r the water. H owever, the composite data from the panel was able to provide co nsistent information that allowed clear trends to be discerned. While individual di fferences in perception of the water quali ty may explain some of the spatial differences evident, there are sufficiently stro ng trends co suggest that there are real differences in the quality of water in different parts of Sale. Such spacial differentiation can only result from the distribution system itself. The mechanism of the alteration is not clear and is worthy of further study. Some preliminary stud ies using UV-Vis absorbance of water have shown sign ificant differences in the absorbance spectra from different pares of the Sale distribution system (Mosse 2003). The study has also shown chat the customer panel were able to detect differences in quality of water resulting from the use of the different bores. This is perhaps surprising since the bores are relatively close together and drawing water from roughly the same depth range and reportedly drawing from the same aquifer. In terms of the preferred treatment regime for Sale, the customer panel identified the low dose chlorine regime and rhe PAC treatment as the preferred treatments. Nor surprisingly rhe low dose chlorine trial produced water with a more acceptable caste and odour profile. Whether rhe Sale system can be run permanently at chis low dose remains to be seen, however since rhe raw water comes from a relatively deep aquifer with a low risk of contam ination by microbiological species it could well be possible. Many European and Scandinavian ground water systems do just chis. PAC treatment also produces palatable water. To introduce permanent dosing of this type would be quite expensive, an d would be introduced as a permanent rrearment only if other mechanisms fail to impro_ve the customers overall perception of rhe water. To chis end the Sale system is currently bei ng run using the most favourable bore and a relatively low chlorine dose of approximately 0.2 mg/L.
108 MARCH 2005
water
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Fig~re 3. Averag ed water quality scores for the different bores used during the period that the plant was operated at 0.35 mg/L free ch lorine.
The ch loraminarion trial was complicated by the fact char, although it was unknown at the time, the initiation of the trial coincided with rhe use of the most unfavourable raw water source. From a purely scientific perspective, rhe trial should be repeated however considerable effort would be required to do this. Should che situation change in rhe future then it may be appropriate to repeat chis process modification. It is also poss ible chat if the chloraminacion trial had been extended the problems may have reduced. Experiences in ocher pares of rhe world have found chloramination to help reduce caste problems of chis type. The resu lts showi ng the different water types in rhe different bores are interesting. While the reason for chis is nor clear, it would seem chat there is a very real possibility chat whatever is causing the 'taint' in the unfavourable bores could eventually appear in the favou rable bore.
T he challenge will be to develop monitoring to detect chis. If and when chis happens, PAC dosing may well become the only option to produce acceptable quality water.
Acknowledgements A project such as this requ ires a ream effo rt. T he authors wish to acknowledge the significant involvement of Joanne Dye, Theresa Garvey, Russell Mack, Trevor Marcin and Ian Soutar. Special thanks are also extended to the people of Sale who wi lli ngly participated in the trial. The Authors Dr Peter Mosse (peter. mosse@ gippswarer.com.au) works part time with Gippsland Water on special projects and also works within the wider water ind ustry providing specialise tech nical assistance in water and wastewater treatment. Jillian Busch (j illian.busch@gippswacer.co m.au) is a Water Quality Technologist with Gippsland Water. References
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H eitz A, Blythe J, Allpike B, Joli CA and Kagi R (2002). Plastic tastes in drinking water: Factors affect ing the chemistry of bromophenol format ion . Proceedings Enviro 2002 Heitz A, Blythe J, Allpike B, Trolio R, Smith R. and Joll C (2003). Factors contributing to bromophenol related tastes in drinking water: Field studies. Proceedings Oz Water 2003. Mosse P. and Bugden K. (2002) Cleaning up a water supply system. Water 29:36-40 Mosse P (2003). Off tastes and distribution systems. Studies using UV Vis Spectroscopy. WaterWorks June 2003: 44-46 NHMRC. (2002) Ausrralian Drinking Water Guidelines. (Draft 2002)
refereed paper