|
Taste,
Odour and Appearance
The human senses of taste
and smell are stimulated by a myriad of chemical
compounds, both organic and inorganic. Certain
of these compounds may be found in private
water supplies, and more than any other factor
they influence the palatability of the water.
Another important aspect
is appearance of the water, it must be at
least clear to be palatable.
Some common pollutants found in wells, springs,
and boreholes which manifest themselves are:
Naturally occurring algae
These range from grassy,
fishy, cucumber, musty, spicy and septic
odours having sweet to bitter tastes and
leave a dry or metallic taste on the tongue.
Typical colours are green,
blue/green to brown and will sometimes produce
a film on the surface looking similar to
oil.
Manganese
This is very abundant in
rocks and soils, it is essential for nutrition
in both plants and animals. However at high
levels of 200 to 400 µg/l will impart
an unpleasant musty/farm taste and can foster
the growth of micro-organisms which will
produce secondary tastes such as pond-like
or earthy.
At concentrations of 500
µg/l the appearance of the water will
be affected. When allowed to come into contact
with oxygen from the atmosphere manganese
will oxidise changing the colour of the
water from clear to grey/brown cloudy.
Iron
This is commonly found,
sometimes in the presence of manganese,
its characteristics are very similar to
manganese, the taste is dry and metallic,
but when oxidised it will usually produce
suspended particles of iron oxide (rust)
which are orange/brown in colour.
Copper:
If acidic water is passed
through copper plumbing, copper is dissolved,
imparting a distinctive blue colour. With
domestic soap, insoluble copper soaps may
be formed, leaving blue/green deposits.
Sulphide and sulphate:
The most common reasons
for Sulphide and Sulphate in ground waters
in the United Kingdom are the natural processes
of organic decomposition and bacterial activity.
However, at low pH levels,
this can produce hydrogen sulphide, which
has a distinctive rotten eggs odour. Sulphate
over 1000 mg/l can exert a laxative effect.
|
