Supply system factors associated with microbiological drinking water safety in regional New South Wales, Australia, 2001-2007.
OBJECTIVE
To determine factors associated with microbiological safety of public drinking water systems in regional New South Wales (NSW), Australia.


METHODS
We analysed 107,000 end-user drinking water samples for an association between detection of Escherichia coli and drinking water system features, sample year and season using NSW Health Drinking Water Monitoring Program data, 2001-2007. We used negative binomial generalized estimating equations with adjustment for autocorrelation and clustering.


RESULTS
We detected E. coli in over 2% of samples from 40% (129/323) of systems. E. coli detection was significantly more common in earlier years and during summer (p<0.001). On multivariate analysis E. coli detection was significantly associated with smaller systems; watercourse sources; no disinfection or disinfection with ultraviolet only; and higher post-treatment mean turbidity (all p< or =0.01). Detection was most strongly associated with lack of disinfection (incidence rate ratio 12.6, p<0.001) and smaller supply systems (1% reduction in E. coli detection for each 1,000 person increase in supply population, p=0.004). Ultraviolet disinfection alone was the least effective disinfection method (p<0.001).


CONCLUSIONS
Even in developed countries, drinking water systems without disinfection or serving small populations appear vulnerable to the effects of faecal contamination, which presents a risk of waterborne disease outbreaks.
NSW Department of Health, NSW Public Health Officer Training Program, Centre for Epidemiology and Research, Locked Mail Bag 961, North Sydney New South Wales, 2059, Australia. mcretikos@optusnet.com.au
Michelle
M
Cretikos
Paul
P
Byleveld
David N
DN
Durrheim
Philippe
P
Porigneaux
Tony
T
Merritt
Sandy
S
Leask
D004755:Enterobacteriaceae / Q000302:isolation & purification; D004926:Escherichia coli / Q000302:isolation & purification*; D006801:Humans; D009517:New South Wales; D012621:Seasons; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods; D014881:Water Supply / Q000032:analysis*