Understanding Water pollution

INTRODUCTION
Water is a basic natural resource required by all human being. Water covers about 70% of the Earth's surface whereas 0.002% of the water is available for human consumption. Contaminated water is the main source of infectious diseases (e.g. Amoebiasis and Malaria, Cholera, Dysentery, Paratyphoid Fever, Typhoid, Jaundice). The WHO reports that one sixth of the world’s population (1.1 billion people) does not have access to safe water. Water pollutions that come from industry, agriculture or households, returns negatively back to the environment. Chemical wastes (e.g. Arsenic, Fluorides, Lead, Nitrates, Pesticides, Petro-chemicals) in the water have negative effect on living organism in water and subsequently on our health. The effects of water pollution are varied and depend on chemicals kinds that dumped and their locations (urban areas are highly polluted). Pollutants such as lead and cadmium are consumed by tiny animals. Later, the food chain continues to be disrupted at all higher levels. Several countries sought to regulate the discharges of pollutants in the water to minimize pollution and contamination through various treatments. In this review, we are going to explain the definitions, types and methods of controlling water pollution to promote sustainable use of water. Moreover, ensuring the highest protection of water from all hazardous chemicals.
Man requires a minimum body intake of water that varies from 2.8 - 13 litres per head per day depending on the climate and the temperature. If there is no intake of water into the body, death can ensue in 7-10 days. Water is also essential to man for maintaining personal hygiene and freedom from disease.
As stated by Wikipedia, Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). Water pollution occurs when pollutants are directly or indirectly discharged into water bodies without adequate treatment to remove harmful compounds.
Water pollution affects plants and organisms living in these bodies of water. In almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities. As we see around the earth, there is plenty of water. Infact 70% of earth is covered with water. But hardly 2% of it is drinkable. We all know that water is very essential for existence of human beings. With the growing population and mismanagement of water resources, scarcity of water has become a bane in India and the rest of the world.Whether it is in use of running water in our homes, rearing cattle and growing crops in our farms, or the increased uses in industry, remain immeasurable. It is important therefore, to note that depletion of this commodity either through contamination, or careless use results in serious consequences.
WHAT IS WATER POLLUTION?
-To the general public, pollution is evident in terms of the observed appearance of the water e.g. A river is polluted if the water is turbid, has foam on the surface, has an objectionable smell, and does not support fish and other living organisms.

• Pollution may also be defined as a natural or induced change in the quality of water which renders it unusable or dangerous as regards food, human and animal health, industry, agriculture, fishing or leisure pursuits.
• Basically water pollution is induced by human activities which cause pollutants to enter natural waters.
  Water pollution may be defined as the contamination of streams, lakes, seas, underground water or oceans by substances, which are harmful for living beings. If the concentration of substances naturally present in water increases then also the water is said to be polluted.
  Water may be called polluted when the following parameters stated below reach beyond
  A specified concentration in water. The following figure shows the major contributors to water pollution

METHODS OF CONTROLLING WATER POLLUTIONS.
a. Setting up of effluent and sewage treatment plants to treat waste water can reduce the pollution load in the recipient water. The treated effluent and domestic water can be reused either for gardening or cooling purposes or wherever possible. Sewage treatment either removes the harmful components or converts them into harmless components.
b. Integrated nutrient management (INM) and integrated pest management (IPM) practices will reduce the effects caused due to excess pesticides.
c. For effective control of water pollution, legal provisions regarding water pollution should be enforced by special administrative machinery comprising of highly qualified and experienced personnel.
Waste water generated by household activity, industries or garbage landfills is called sewage which is classified as the municipal water pollution. Sewage contains solid matters in the form of suspended colloidal and dissolved organic matter, detergent, mineral matter, nutrients and gases. Sewage is one of the major causes of water borne diseases and therefore the treatment of sewage is one of the important tasks. For a long time treatment of municipal waste in the form of sewage involved mainly of the removal of suspended solids, oxygen demanding materials and harmful bacteria. Now the disposal of the solid residue from sewage has been improved by applying municipal treatment processes.
Treatment of Domestic Sewage: Domestic sewage can be purified even to make it suitable for drinking; however the process is expensive. Usually, treatment of sewage to reduce its organic matter content is adopted. In this treatment, three steps are involved:
Step 1: Primary Treatment:
In this step the following are affected:
(a) Large objects are trapped.
(b) Dust, grease, scum are removed.
(c) Biochemical Oxygen Demand (BOD) is removed.
(d) Suspended matter is made to settle down by passing water through the gut chamber.
Step 2: Secondary Treatment:
In this step, following are affected:
(a) BOD is further reduced.
(b) By aeration using a trickling filter, aerobic organisms are grown to decompose pollutants.
(c) The water at the end of this step can be used for irrigation and in industries.
Step 3: Tertiary Treatment:
In this expensive step:
(a) Organic chemicals and nutrients are removed.
(b) The dissolved organic salts are removed using coagulation or distillation or reverse osmosis.
(c) Pathogens are destroyed by disinfection.
The water after this treatment is fit for groundwater recharge. After chlorination and proper check, it can be used for drinking.