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.
Cretikos
Michelle
M
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
Byleveld
Paul
P
Durrheim
David N
DN
Porigneaux
Philippe
P
Merritt
Tony
T
Leask
Sandy
S
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*