Waterborne Disease Outbreaks and the Multi-barrier Approach to Protecting Drinking Water - Global Drinking Water Management and Conservation - page 21

2.3.2 Escherichia Coli

Escherichia coli is a well-known drinking water contaminant because of the highly
publicized drinking water contamination that occurred in Walkerton, Ontario,
Canada in 2000. E. coli, similar to Campylobacter, is a bacterial pathogen that is
not resistant to chlorine disinfection. E. coli contamination could be easily pre-
vented particularly in smaller rural communities, since chlorine is the most com-
monly used chemical disinfection for drinking water. Groundwater in the
Walkerton case became contaminated with several pathogens, but primarily E. coli
and Campylobacter jejuni, causing over 2,300 cases of illness and seven deaths in
the community of approximately 4,800 people (Hrudey et al. 2002 ,p.397 398).

The source of the contamination was cattle manure. It occurred through a combi-
nation of heavy rainfall causing the runoff into the water source, and also system
de

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ciencies such as human error; the water system managers did not detect the
contamination, and therefore did not treat it. The Walkerton Inquiry was com-
missioned following the outbreak, and was released in 2002. The Inquiry discussed
the reasons and causes of the outbreak, and also provided recommendations for new
and existing legislation to prevent future occurrences. The Inquiry emphasized the
necessity of the multi-barrier approach to provide safe drinking water. A common
theme among the research on drinking water outbreaks is the failure of barriers in
water systems, allowing contaminations to occur and pass through distribution
systems to cause illness. System de ciencies, including treatment and operational

failures, were the main reasons for the Walkerton outbreak of 2000.
Another case of E. coli contamination occurred earlier in Cabool, Missouri in
1989, prior to the Walkerton contamination. The small rural community of
approximately 2,090 people reported 243 cases of illness and four deaths. Although
not as publicized as the Walkerton incident, Cabool

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cant
as it also caused death. Cabool uses a groundwater source, but direct source con-
tamination was not believed to have occurred. The source of contamination is
believed to have been fecal contamination from sewage. It occurred from a lack of
disinfection following replacement of water meters and repairs to broken water
mains. Unseasonably cold weather caused the water mains to break. The sanitary
sewer system was also vulnerable to storm runoff (Hrudey et al. 2002 , p. 403). The
introduction of chlorination into the system subdued the outbreak (Rice et al. 1992 ,
p. 38). Again, similar to Walkerton, this outbreak was due to system de

s outbreak was also signi

ciencies.
Treatment, particularly disinfection, is critical to ensure safe drinking water. Proper
chlorination would have been effective against the E. coli contamination and would
have prevented the outbreak.
In both outbreaks of E. coli, loss of life was associated with the contamination.
The severity of the outbreaks emphasizes the need for adequate treatment, opera-
tional practices, and the maintenance and upkeep of equipment. A common thread
between the bacteria pathogens, Campylobacter and E. coli, is that outbreaks most
commonly occur in communities with surface sources or groundwater supplies that
can come under the in

uence of surface water and there is inadequate disinfection.