Water Pollution

WATER POLLUTION

          Water pollution refers to the undersirable change occurring in water which may harmfully affect the life activities of man and domesticated species.

Water pollutants:  The common water pollutants are as follows.

·       Domestic sewage

·       Industrial effluents

·       Pesticides

·       Fertilizers

·       Micro organisms

·       Plankton blooms

·       Heavy metals

·       Temperature

·       Silt

·       Radioactivity

·       Oil

 

Causes of Water Pollutants

1.   Domestic sewage:  The sewage is released into the river.  It consists of human face, urine and dirty particles used up in houses.  It contains large number of pathogenic bacteria and virus.

2.   Industrial effluents:  The non-usable organic and inorganic chemical waters released from the industries are get into water bodies.  These wastes includes heavy metals, detergents, petroleum, carbonates, cyanides, chlorine

3.   Thermal pollution:  Many industries use water for cooling.  The resultant warm water is discharged into rivers.  It brings about thermal pollution.

4.   Pesticides:  These are chemicals used to control pests in crop fields and houses.  They include DDT,  BHC, Endrin etc.

5.   Fertilizers:  The fertilizers used for crops are washed into ponds and rivers.

6.   Radioactive wastes:  Liquid radioactive wastes released into the sea around nuclear installations.  The oceanic currents carry the radioactive contamination every where.

7.   Oil pollution:  Oil is a source of pollution in sea water.  Oil pollution is due to ship accidents, loading and discharging of oil at the harbor and oil refineries.

8.   Retting:  The process of decaying coconut just to get fibre for making coir is called retting.  Retting releases h2s.  It is toxice and makes water polluted.

Ecological effects of water pollution

1.  Minamata disease:  This disease is caused by mercury poisoning.  It is characterized by crippling and death.  This disease appeared in a coastal town, Minamata in Japan,  Mercury, a by product released from plastic industry was disposed into  the sea.  The accumulation of mercury leads to crippling and death.  The initial symptoms of minamata disease includes numbness of limbs, lips and tongue, impairment of motor control deafness and blurring of vision.  Finally it affects the brain.

2.  Diarrhoea:  It is caused by micro organisms and metals like mercury, cadmium and cobalt.  Some of the diseases caused by microbes and metals found in water are as follows.

·       Typhoid fever

·       dysentery

·       hookworm disease

·       whooping cough

·       methamoglopinema

·       jaundice

·       poliomyelitis

·       pneumonia

·       influenza

·       handy code syndrome

3.  Mortality of plankton and fish:  Chlorine which is added to water to control the growth of algae and bacteria in the coding system of power stations may persist in streams to cause the mortality of plankton and fish.  Plankton is a small aquatic plant or animal that live in the surface water.

4.  Reduction in productivity:  Intensive agriculture increases the amount of silt in lakes and rivers.  Silt reduces transparency of water and prevents the penetration of light to depths and reduces primary production.

5.  Siltation:  Siltation is a phenomenon by which the gills of fishes are deposited with silt.  This causes heavy mortality among fishes.

6.  Poor oxygenation:  Oil present on the surface of water prevents water oxygenation.  This reduces respiration and metabolism in aquatic organisms.

7.  Poor photosynthesis:  Oil pollution prevents photosynthesis in phythoplankton.

8.  Red tide:  When coastal waters are enriched with nutrients of sewage, dinoflagellates multiply rapidly and form bloom.  These blooming dinoflagellates produce toxic metabolic by products which can result in a large scale death of marine fishes.  This is called red tide.

9.  Biochemical oxygen demand:  Sewage enriches the water with nutrients.  This causes growth of plankton and algae.  This leads to oxygen depletion in water.  This depletion causes the death of algae.  The decay and decomposition of algae consume more oxygen from water.  Biological oxygen demand is the amount of oxygen required by the microorganisms in water.  BOD is higher in polluted water and lesser in drinking water.

10.  Water-borne diseases:   Diseases like jaundice cholera, typhoid, diarrhea are transmitted through water contaminated with sewage.

11.  Methacmoglobinema:  The nitrate used in fertilizers enters the intestine of man through drinking water,  In the intestine, it is converted into nitrite,  Nitrite is absorbed into the blood where it combines with haemoglobin to form met haemoglobin.  Met haemoglobin cannot transport oxygen.  This leads to suffocation and breathing troubles,  especially in infants.  This disease is called methaemoglobinema.

12.  Eutrophication:  The increased productivity of lakes and ponds brought about by nutrient enrichment is known as eutrophication.  Domestic sewage and fertilizers add large quantities of nutrients such as nitrates and phosphates to the fresh water ecosystems.  The rich supply of these nutrients make blue green algae, green algae and other phytoplankton to grow abundantly.  As the algae use O2 of the water for respiration, the O2 is depleted from the water.  Thus eutorphication leads to the complete depletion of the flora and fauna from the ecosystem.