Biology Reference
In-Depth Information
must be updated at least every 2 years. 33 Tanks storing drinking water are
also required to be cleaned at least once a year within the DWI guidelines,
with an inspection also to be carried out on a six-month basis. 33
There is a variety of legislation to control exposure to Legionella in the
UK, including the coverage in the Health and Safety at Work Act 1974,
which requires monitoring and inspections as well as approved codes of
practice for water systems in the work place. However, there are no stan-
dards for detecting, or removing, Legionella in the drinking water in the
UK, due to the fact that risk from drinking water is deemed low. Potable
water supplies are not considered the primary cause of the bacteria's spread,
so water itself is not treated for Legionella pathogens. Instead, focus is kept
on maintaining facilities and equipment for water supply and storage and
preventing the growth of these bacteria in the first place.
11.4.3. Giardia lamblia
Giardia lamblia is a single-celled protozoan parasite that can be found in
water that has been contaminated by feces, either from infected humans or
animals. If the protozoan is transmitted to humans through contaminated
water, it can cause “giardiasis”, which includes symptoms such as acute or
chronic diarrhea, weight loss, abdominal pain and nausea. The threat of the
spread of Giardia in UK water is considered to be very low due to the
sufficient treatment of supplies. The cysts are resistant to two of the most
common water treatment methods, namely chlorination and ozonolysis.
Filtration systems such as “slow sand filters” with a filter that has a nominal
1-µm pore size have been shown to help remove up to 99% of Giardia cysts
in water pretreatment, but processes of chemical oxidation of water supplies
is effectively able to remove the cysts as well.
11.4.4. Escherichia coli
Escherichia coli , commonly known as E. coli , is another pathogen potentially
found in drinking water supplies. Escherichia coli are bacteria found in human
or animal intestines. Toxic strains of E. coli can cause serious illness, which
can result in severe diarrhea and even kidney damage in some cases. 34 The
bacteria can potentially be passed to humans through contaminated water
supplies. If any E. coli is detected in UK drinking water supplies, an inves-
tigation will be undertaken to identify and eliminate the source. Escherichia
coli in the UK is associated considerably more with contaminated food than
with water supplies, but outbreaks have been detected in water, particularly
from private supplies. 28 The bacteria itself will usually be removed during
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