Water, Sewage & Effluent July August 2018 | Page 32

Faecal coliform bacteria
recommendations
• 
Body-contact recreation: fewer
than 200 colonies/100mℓ
• 
Fishing and boating: fewer than
1 000 colonies/100mℓ
• Domestic water supply, for treatment
(Odonkor & Ampofo, 2013): fewer
than 2 000 colonies/100mℓ.
• Drinking water standard: less than
1 colony/100mℓ.
Faecal coliform bacteria
in streams
Why is it important?
Because faecal coliform bacteria
are microscopic organisms that live
in the intestines of warm-blooded
animals, they also live in the waste
material, or faeces, excreted from the
intestinal tract. When faecal coliform
bacteria are present in high numbers
in a water sample, it means that the
water has received faecal matter
from one source or another. Although
not necessarily agents of disease,
faecal coliform bacteria may indicate
the presence of disease-carrying
organisms, which live in the same
environment as the faecal coliform
bacteria.
Swimming in water with high levels
of faecal coliform bacteria increases
the chance of developing illness (fever,
nausea, or stomach cramps) from
pathogens entering the body through
the mouth, nose, ears, or cuts in the
skin. Diseases and illnesses that can
be contracted in water with high faecal
coliform counts include typhoid fever,
hepatitis, gastroenteritis, dysentery,
and ear infections.
Reasons for natural
variation
Unlike the other conventional water
quality parameters, faecal coliform
bacteria are living organisms. They do
not simply mix with the water and float
straight downstream. Instead, they
multiply quickly when conditions are
favourable for growth or die in large
numbers when conditions are not.
Because bacterial concentrations are
dependent on specific conditions for
growth, and these conditions change
quickly, faecal coliform bacteria
counts are not easy to predict. For
example, although winter rains may
30
wash more faecal matter from urban
areas into a stream, cool water
temperatures may cause a major
die-off. Exposure to sunlight (with its
ultraviolet disinfection properties)
may have the same effect, even in the
warmer water of summertime.
Expected impact of
pollution
The primary sources of faecal
coliform bacteria to freshwater
are wastewater treatment plant
discharges, failing septic systems, and
animal waste. Bacteria levels do not
necessarily decrease as a watershed
develops from rural to urban. Instead,
urbanisation usually generates new
sources of bacteria. Farm animal
manure and septic systems are
replaced by domestic pets and leaking
sanitary sewers. In fact, stormwater
run-off in urbanised areas has been
found to be surprisingly high in faecal
coliform bacteria concentrations. The
presence of old, disintegrating storm
and sanitary sewers, misplaced sewer
pipes, and good breeding conditions,
are common explanations for the high
levels measured.
Faecal coliform concentrations
are reported in un