Waterborne Disease Outbreaks and the Multi-barrier Approach to Protecting Drinking Water - Global Drinking Water Management and Conservation - page 24

This survey of waterborne disease outbreaks makes it clear that outbreaks can occur
in both large and small communities. As mentioned above, Milwaukee with a larger
population of 840,000 served by the water system and North Battleford with a
smaller population of 15,000, have both experienced outbreaks of cryptosporidio-
sis. The major difference is that an outbreak among a larger population is likely to
have a more signi cant impact, as more people are affected. The outbreaks that

have occurred after Walkerton in 2000 also indicate that large communities are also
susceptible to contamination.
Another factor that seems to stand out in the outbreaks is the reliance on
chlorine. Communities that rely heavily and especially those that rely solely on
chlorine disinfection are vulnerable to contamination. This chapter suggests that the
most dominant microbial contaminant of the outbreaks referred to here is a pro-
tozoan pathogen, namely Cryptosporidium. The ability of protozoa to in

ltrate and
pass through many drinking water systems is because of their resistance to chlorine.
Alternative treatments that are effective against protozoa are filtration, ozone

treatment, and UV light treatment. Communities that have experienced problems of
Cryptosporidium contamination often rely heavily or solely on chlorination. This is
a signi

cant limitation in the use of chlorine. Another disadvantage of chlorine is
the byproducts that can result from its use. Trihalomethanes (THMs) form through a
reaction between chlorine and organic compounds. These are known as disinfection
by products (DBPs) and can have long-term health effects (Moghadam and Dore
2012 ). Chlorine can also create a distinctive taste if high levels of disinfection are
required, which is often strongly disliked by receiving communities. Alternative
methods of disinfection should be considered to avoid the problem of ineffective
disinfection and the occurrence of THMs.
Multi-use watersheds involve a variety of activities and operations that could all
contribute to a contamination. It is clear that farming operations often result in
animal fecal matter contaminating water courses. Sewage treatment plants are
another common cause of contamination. Animal and human fecal matter is the
most common source of contamination in the drinking water outbreaks. The
increase of human activity in a watershed also increases the possibility of con-
tamination. Consequently multi-use watersheds need to increase the scrutiny of
their water quality.
Boil water advisories (BWAs) are issued in order to prevent disease and
drinking water outbreaks. A BWA requires all citizens of the speci ed community

to boil their water prior to consumption in order to kill the possible pathogens
within the water. BWAs are issued at the local level by the water authority of a
community often following the detection of contamination, as a precautionary
measure. Used wisely a BWA can prevent an outbreak. A BWA is effective when
the detection of a pathogen in a water system is con rmed. However, a BWA can

be ineffective when uncertainty of the water quality results in a continuous use of
BWAs. A BWA is also ineffective when it is used as an alternative by water
systems rather than providing the necessary treatment and equipment maintenance
to be able to supply safe drinking water. A BWA should not be issued to avoid the
responsibility of proper treatment and maintenance, but continuous and long-