A boy collect plastic waste in the River Buriganga.
After oxygen, water is the most vital substances to sustain life on
earth. Its supply is also abundant. Covering almost 70 percent of the
earth's surface, this compound rules every step of our life. A drop of
water is simply another name for life. A molecule of this life
sustaining compound is made of one oxygen atom and two hydrogen atoms.
But
this water can become life-threatening. With the increasing rate of
pollution, water has become a serious health hazard for us. Moreover,
the sustainability of water resources is becoming a major issue. To
increase public awareness about the water-related problems as well as to
promote several activities on water resources, a day has been set by
the UN as the World Water Day with a theme selected for each year. The
observance of the day began from March 22 since 1993
Water
pollution has a wide definition, which may be described as any physical,
chemical or biological change in water quality that adversely affects
living organisms, or makes water unsuitable for its desired uses. This
pollution may be caused by two processes- natural and anthropogenic or
man made processes. At present, natural pollution of water is
insignificant compared to its anthropogenic pollution.
Surface
water bodies, such as rivers, streams and lakes, support a variety of
life forms including fish, whose ability to survive in their natural
habitat is dependent on the quality of water in these water bodies. This
water quality is mainly determined by one common indicator called
Dissolved Oxygen or DO. DO means the sufficient amount of oxygen needed
for aquatic life. It is the parameter which represents the purity of
water. The reduction in the level of DO significantly hampers normal
aquatic life, thus threatening the whole ecosystem indirectly.
Pollution
of surface water bodies results from the discharge of wastes from a
variety of sources including municipal sewage, industrial wastewater and
agricultural wastewaters. The wastes that are discharged into these
water bodies may include organic wastes, persistent chemical wastes,
heat wastes, radio wastes etc. By far the greatest volume of discharge
into rivers and streams is that of oxygen demanding organic waste that
consumes the available DO in oxidizing the waste.
When oxygen
demanding wastes are discharged into a river or stream, the rate at
which oxygen is consumed in oxidizing that waste may exceed the rate at
which oxygen is replenished from the atmosphere. This can lead to
depletion of oxygen resources, with DO concentrations falling far below
the required levels. When this level drops below 4-5 milligram per
liter, reproduction by fish and other macro organisms is impacted.
Further depletion of DO may lead to anaerobic conditions with loss of
biotic diversity.
The water pollution problem in Bangladesh has
become a topic of great concern. A study shows that about 80 million
people from Bangladesh are exposed to a high level of toxicity from the
water contaminated with arsenic. The situation is even worse in the
capital Dhaka. According to a study conducted by World Bank, four major
rivers near Dhaka -- the Buriganga, Shitalakhya, Turag and Balu -receive
1.5 million cubic meters of wastewater every day from 7,000 industrial
units in surrounding areas and another 0.5 million cubic meters from
other sources. The Buriganga , which was the pride of Dhaka, is now one
of the most polluted rivers in Bangladesh because of careless dumping of
industrial and human waste. Serious water-borne diseases are taking
away many precious lives. All we can hope is an active step against
these pollutions. The success of water day will depend on that.
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