Waterborne Disease Outbreaks and the Multi-barrier Approach to Protecting Drinking Water - Global Drinking Water Management and Conservation - page 15

signi cance caused changes within the regulation of drinking water in the United

States. After the outbreak, the US Environmental Protection Agency enacted the
Surface Water Treatment Rule (SWTR). The rule required both disinfection and

filtration of all surface waters, as well as groundwaters that are affected by surface
waters (Rose 1997 , p. 154). Also following the outbreak stricter practices were
imposed for chemical dosing and filter monitoring, and long-term improvements

were achieved by installing an ozone disinfection facility. Therefore, it can be
assumed that the level of

filtration and its monitoring must have been inadequate, as
it should have been effective at removing or inactivating the contaminant. The
contaminants were able to enter the surface source and were also able to pass
through the treatment process into the distribution system without detection.
In March 1993, Kitchener/Waterloo Ontario experienced an outbreak of 1,000
cases of cryptosporidiosis. The contamination occurred when the region of
approximately 390,000 people switched from a Cryptosporidium-free groundwater
source to a contaminated surface water source, the Grand River (Frost et al. 1997 ,
p. 10). A newly constructed filtration plant was being used for the conventional

treatment of the surface water, with also ozonation treatment. Several other com-
munities had been using the river as a source of water for a number of years, and
had not experienced an outbreak. It has been suggested in the literature that this
may be related to the low immunity to Cryptosporidium that occurs from drinking
from groundwater sources (Frost et al. 1997 , p. 10). The source of the contami-
nation is believed to have been recycled backwash waters, as suspected in
Milwaukee (Rose 1997 , p. 141). In the presence of a contaminant, cleaning with
backwash water may reintroduce the pathogen into the system. The signi cance of

this outbreak is that it occurred in a large municipality, compared to the majority of
drinking water outbreaks that occur in small rural communities.
In 1996, two communities in British Columbia experienced outbreaks of cryp-
tosporidiosis. The

first occurred in May in the city of Cranbrook, which has a
population of 18,131, causing approximately 2,000 cases of illness. The second
occurred shortly afterwards in June in the city of Kelowna, which has a population
of 89,442, causing 10,000

15,000 cases of illness. Cranbrook is in the area of
southeastern B.C., while Kelowna is in central B.C., 271 km away from Cranbrook
(Ong et al. 1999 , p. 64). Both cities use surface water sources. Cranbrook uses
Joseph Creek and Gold Creek, and Kelowna uses Okanagan Lake. Also, both cities
use the same treatment method of only chlorine, without

-

filtration. The majority of

water systems in BC are un ltered and the water is drawn from surface sources, and

most also rely on chlorination for simple disinfection (Ong et al. 1999 , p. 67). This
is a primary concern because of the vulnerability of surface water to contamination.
Chlorine is ineffective against protozoan pathogens such as Cryptosporidium, and
therefore alternative treatment methods, such as filtration, are necessary. The source

of contamination in both cases is believed to have been runoff of cattle manure
(Ong et al. 1999 , p. 63). Treatment failure was the cause of this outbreak because of
reliance on chlorine alone. Following the outbreak, the City of Cranbrook decided
not to install a

filtration plant, but instead has placed monitors into the creeks.
Kelowna took more action, possibly because of its larger population and the greater