Water Pollution :
Water pollution may be defined as , " the alteration in physical, chemical, and biological characteristics of water which may cause harmful effects on humans and aquatic life."
The pollutants include sewage, industrial chemicals and effluents, oil and other wastes. Besides, chemicals from the air dissolved in rain waste, and fertilizers, pesticides and herbicides leached from the land also pollute water.
Types, Effects and Sources ( causes ) Of water Pollution :
Water Pollution is any chemical, biological or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses.
1. Infectious Agents :
Examples - Bacteria, Viruses, Protozoa and Parasitic worms.
Human Sources :
Human and Animals wastes.
Effects :
Variety of diseases.
2. Oxygen Demanding Wastes ( Dissolved oxygen ) :
Examples : Organic wastes such as animal manure and plant debris that can be decomposed by aerobic (oxygen - requiring) bacteria.
The degradation consumes dissolved oxygen (DO) is the amount of oxygen dissolved in a given quantity of water at a particular pressure and temperature.
The saturated point of DO varies from 8 -15 mg / lit.
Human Sources ( Causes ) :
Sewage, animal feed lots , paper mills, and food processing facilities.
Effects :
Large populations of bacteria decomposing these wastes can degrade water quality by depleting water of dissolved oxygen. This causes fish and other forms of oxygen - Consuming aquatic life to die.
3. Inorganic Chemicals :
Examples : Water Soluble Inorganic Chemicals.
i) Acids,
ii) compounds of toxic metals such as lead (Pb), arsenic (As) and Selenium (Se) and
iii) salts such as Na cl in ocean water and fluorides (F-) found in some soils.
Human Sources :
Surface runoff, industrial effluents and household cleansers.
Effects :
i) Can make fresh water unusable for drinking or irrigation.
ii) Causes skin cancers and neck damage.
iii) Damage the nervous system, liver and kidneys.'
iv) harm fish and other aquatic life.
v) Lower crop yields.
vi) Accelerates corrosion of metals exposed to such water.
4. Organic Chemicals :
Examples : Oil , gasoline, plastics, pesticides, cleaning solvents, detergents.
Human Sources (Causes) :
Industrial effluents , household cleansers, surface runoff from farms.
Effects :
i) Can threaten human health by causing nervous damage system damage and some cancers.
ii) Harm fish and wild life .
5. Plant Nutrients :
Examples - Water- soluble compounds containing nitrate (NO-3), phosphate , and ammonium (NH+4) ions.
Human Resources :
Sewage, manure, and runoff of agricultural and urban fertilizers.
Effects :
i) Can cause excessive growth of algae and other aquatic plants, which die, decay, deplete dissolved oxygen in water and kill the fish.
ii) Drinking water with excessive levels of nitrates lower the oxygen carrying capacity of the blood and can kill urban children and infants.
6. Sediments :
Examples - Soil, Silt etc.,
Human Sources ( Causes )
Land erosion.
Effects :
i) Can reduce photosynthesis and cloud water.
ii) Disrupt aquatic food webs.
iii) Carry pesticides, bacteria, and other harmful substances.
iv) Settle out and destroy feeding and spawning rounds of fish.
\v) Clog and fill lakes, artificial reservoirs, stream channels and harbors.
7. Radioactive Materials :
Examples - Radioactive isotopes of iodine, radon, uranium, cesium, and thorium.
Human Resources (Causes) :
Nuclear power plants, mining and processing of uranium and other ores, nuclear weapons production and natural resources.
Effects :
Genetic mutations, birth defects, ands certain cancers.
8. Heat ( Thermal Pollution ) ;
Examples - Excessive heat
Human Sources ( causes ) :
Water cooling of electric power plants and some types of industrial plants. Almost half of all water withdrawn in United states each year is for cooling electric power plants.
Effects :
i). Lowers dissolved oxygen levels and make aquatic organisms more vulnerable to disease, parasites and toxic chemicals.
ii). When a power plant first opens or shuts down for repair, fish and other organisms adapted to a particular temperature range can be killed by the abrupt change in the water temperature known as thermal shock.
9. Point and Non - Point Sources of Water Pollution :
i) Point Sources :
Point Sources are discharged pollutants at specific locations through pipes, ditches or sewers into bodies of surface water.
Examples - Includes factories, sewage treatment plants, abandoned underground mines and oil tankers.
ii) Non Point Sources :
They are usually large land areas or air sheds that pollute water by run off., subsurface flow or deposition from the atmosphere. Location of which cannot be easily identified.
Examples - Include acid deposition and runoff of chemicals into chemicals into surface water from croplands, livestock feedlots, logged forests, urban street, lawn , golf courses and parking lots.
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