Water pollution occurs when quality of a water body is changed as a result of the entry of harmful substances.
More often than not these harmful substances come from man’s activities. Pollution of this nature makes streams, lakes an coastal waters unpleasant to look at, to smell and to swim in. Fish and other sea animals harvested from such waters are to eat. People who drink polluted waters can become ill and with prolonged exposure may even develop cancer.
All living things contain it and it provides a home for many kinds of life.
70% of the earth’s surface is covered with water in the form of oceans, seas, rivers, streams etc with the vast majority in the form of salt water and very small amount of fresh water. Humans can only use fresh water.
Fortunately for all living things, water is recyclable in nature i.e. it is a renewable resource.
But, this natural process takes time and is dependent on climatic conditions .
Many industries discharge wastes directly into waterways. As the waste builds up, the water develops a foul odor. The building of waste also causes the amount of O2 in the water to drop, leading to the death of aquatic organisms.
Some industries also burn coal, oil and other fuels. This releases sulphur and nitrogen oxides into the air. These gases reacts with water in the atmosphere forming acids which return to the earth when it rains in the form of acid rain.
As acid rain drains into rivers and other waterways, fish, algae and other aquatic life may die or be drastically reduced in numbers.
On farms, large amounts of fertilizers and pesticides are applied. When it rains, these chemicals along with the soil drain into nearby trenches, canals and rivers, adversely affecting aquatic life and human health.
Sometimes, these chemicals seep deep into the soil entering the ground water system while the sediments cause the waterways to become cloudy and muddy.
Wastes generated from households are also disposed of in nearby drains.
Garden chemicals, if not properly stored, oils from cars and acid from batteries can enter into nearby waterways. Most visible is the rubbish especially plastic and glass that are dumped into trenched and canals.
Households that rear animals on a small scale also produce animal waste which when disposed of in waterways has the same effect as fertilizers and raw sewage.
Polluted water is dangerous to human health. People who drink polluted water become infected by waterborne diseases such as cholera, diarrhoea or typhoid.
Affects vital body organs
Harmful chemicals in polluted water prevent the proper working of the vital body organs such as the heart and kidney.
Causes toxic buildup in the food chain
Harmful chemicals such as pesticides from agriculture and heavy metals like lead and mercury from industries can build up in the food chain, where they reach toxic levels in fish and other sea animals.
Wastes like urea, animal manure, vegetable peeling provide food for tiny plants called algae. The more waste there is the more algae grows, this is algal bloom. Bacteria feed off rotting algae will in turn consume O2 in the water. As a result, fish and other type of aquatic animals will die as a result of lack of O2.
When a lot of soil is washed away into rivers and trenches, this not only causes aquatic life to perish but also floods especially with heavy rainfalls.