Water pollution is a burning issue of today’s twenty first century. Among four different pollutions, it is also the one which is caused by the addition of unwanted materials into water and its sources. It can be defined as the change in the physical and chemical properties of water due to addition of inorganic matters, organic matters and microorganisms into water bodies. This is very much harmful for health. It also reduces the usefulness of water.
Sources of Water Pollution
The major sources of water pollution are listed below:
Major Pollutants of Water Pollution and their consequences
- Sewage and domestic wastes: Sewage can be defined as the liquid waste which is discharged from all the domestic and industrial sources. About 75% of water pollution is caused by domestic waste and sewage. It causes spreading of different water-borne diseases like cholera, typhoid, hepatitis or jaundice etc. It also kills different aquatic animals and destroys the biological activities. Water reservoirs always maintain a balance between available oxygen and decomposition of organic matters. This capacity is lost due to addition of excess sewage and other wastes. The rate of re-oxygenation becomes slower than the rate of deoxygenation. This activity leads to develop maximum Biological Oxidation Demand (BOD). Biological Oxidation Demand is defined as the amount of oxygen required for biological oxidation by microorganisms present in water bodies. Biological Oxidation Demand is taken as indicator of degree of pollution. The Biological Oxidation Demand value in clean water is about 1 to 2 gram per litre.
- Household detergents: Household detergents are used for washing clothes and cleaning utensils in almost all houses of modern era. These are released into drains which ultimately carry them to water sources like lakes, ponds, rivers, streams etc. The major constituents of detergent include inorganic phosphates and nitrates, ammonium, Alkyl Benzene Sulphonate (ABS). Alkyl Benzene Sulphonate is non-biodegradable and gets accumulated in water bodies which generally form foam over water surface. This causes obstruction to aquatic animals and plants, especially for respiration.
- Inorganic phosphates and nitrates: Phosphates and nitrates stimulate the growth of algae and cover almost all parts of the water surface. This excess growth of algae is called algal bloom. At the same time, algae release toxins which are very much harmful for aquatic organisms. This causes the death of organisms and as a result, large amount of organic matters get deposited in the water bodies. Water bodies rich in such organic matters are called eutrophics. And this process is called eutrophication. The organic matter is decomposed by microorganisms leading to scarcity of oxygen and more carbon dioxide in water. This further causes to death of aquatic animals.
- Industrial wastes: Industries like diary, paper mills, automobile workshops, plasticware factories, textiles etc. produce wastes which are sent into the drains which ultimately carry these effluence to water reservoirs. These wastes contain suspended dust, coal, ash etc. Poisons like acids, mercury, copper, zinc, arsenic, inorganic reducing substances like ferrous salts, sulphides etc. are also released. Different acids, alkalis, lead etc. reduce the oxygen transporting capacity of blood in human body.
- Oils: Oils leaked or spilled from the oil tankers , washing of automobiles etc. make water sources polluted. These activities affect the aquatic animals badly and even degrade the quality of water. They also kill aquatic vegetation and plants near the coastal areas.
- Agro-chemicals: Different agro-chemicals like pesticides, insecticides and chemical fertilizers are used by farmers in their fields for better productivity. These chemicals are washed into different water sources with the help of rain water. These substances are taken up by many organisms through food chain which degrades the health of the organisms.
Control Measures of Water Pollution
The ways to control water pollution are given below:
- Cleaning and treatment of drainage water, septic tanks, oxidation ponds etc. are used to reduce the amount of organic substances. There are two ways of treatment for sewage, they are: primary treatment and secondary treatment. Primary treatment includes physical processes like sedimentation, filtration, floatation etc. Similarly, secondary treatment includes the use of microorganisms in oxidation ponds. Reverse osmosis is newly introduced technique which helps in recycling water into pure and clean form.
- Recycling of waste products should be done.
- The use of pesticides, insecticides and chemical fertilizers should be minimized.
- Another effective method to control water pollution is the treatment of factory effluent in a way that only harmless substances are released.
- Awareness programmes about water pollution and its effects can be conducted.
- Laws should be made and enforced strictly.