INTRODUCTION
Water is that chemical substance which is
essential for every living organism to survive
on this planet. Water is needed by every cell of
the organism’s body to perform normal function.
Water covers 71% of the Earth’s surface, mostly
in oceans and other large water bodies, with 1.6%
of water below ground in aquifers and 0.001% in
the air as vapor, clouds and precipitation (U.S.
Geological Survey 2000). Water moves conti-
nually through a cycle of evaporation or transpi-
ration (evapotranspiration), precipitation, and
runoff, usually reaching the sea. Winds carry
water vapor over land at the same rate as runoff
into the sea. Over land, evaporation and
transpiration contribute to the precipitation over
land. Clean, fresh drinking water is essential to
human and other life. Some observers have
estimated that by 2025 more than half of the world
population will be facing water-based vulnera-
bility, a situation which has been called a ‘water
crisis’ by the United Nations (Kulshre-shtha
1998). A recent report (November 2009) suggests
that by 2030, in some developing regions of the
world, water demand will exceed supply by 50%
(Charting Our Water Future 2009).
Pure uncontaminated water does not occur
in nature. Water pollution is any undesirable
change in the state of water, contaminated with
harmful substances. It is the second most impor-
tant environmental issue next to air pollution.
Any change in the physical, chemical and
biological properties of water that has a harmful
effect on living things is termed as ‘water
pollution’ (WHO 1997). As a result of the unwan-
ted human activities, water pollution is a growing
hazard in many developing countries. A more
serious aspect of water-pollution is that which
is caused by human activity, and industrialization
(Park 2009). There are also various micro-biolo-
gical agents that include bacteria, viruses and
protozoa which can also cause water pollution
and may cause various water-borne diseases