Surface water includes river, lake and pond water but here only river water pollution is discussed as lake water pollution is discussed separately.
Major River Water Pollutants:
Infectious agents include germs and viruses which causes several types of diseases like typhoid, dysentery, cholera, etc.
Plants nutrients and dissolved substances e.g. chemical fertilizers, detergents, etc.
Particulate Matter e.g. soil and mineral particles
Radioactive Substances released from nuclear reactors
Mineral and Chemical Substances coming from industries and mining operations
Thermal e.g. hot water released by power plants, nuclear reactors, industries, etc.
Organic chemical exotics such as synthetic materials like pesticides, insecticides, etc.
Sources of River Pollution
Point Pollution: The main sources of point pollution of river waters are industrial and urban centers.
Sewage water when discharges from houses, commercial and industrial establishments connected to public sewerage system.
The sewage contains human and animal excreta, food residues, cleaning agents, detergents and other wastes.
Domestic and hospital sewage contain many undesirable pathogenic microorganisms.
However, about 70% of the eﬄuents are not treated and disposed oﬀ into the environmental media untreated.
The industries discharge several inorganic and organic pollutants, which may prove highly toxic to living beings.
Discharge of wastewater from industries like petroleum, paper manufacturing, metal extraction and processing, chemical manufacturing, etc.that often contain toxic substances, notably, heavy metals (defined as elements with density > 5 g/cm3 such as mercury, cadmium, copper, lead, arsenic) and a variety of organic compounds.
Geogenic contaminants: salinity, iron, ﬂuoride, and arsenic
Plastic bags are not biodegradable, clog waterways, spoil the landscape; break down into ever smaller particles that continue to pollute the soil and water.
Non-Point Pollution: discharge of pollutants from diffuse sources or from a larger area such as runoff from agricultural fields (agricultural runoff), grazing lands, construction sites, abandoned mines and pits, roads and streets.
Agricultural runoff contains dissolved salts such as nitrates, phosphates, ammonia and other nutrients, and toxic metal ions and organic compounds.
Excess fertilizers and pesticides may reach the ground water by leaching or may be mixed with surface water of rivers, lakes and ponds by runoff and drainage.
Animal excreta such as dung, waste from poultry farms, piggeries and slaughter houses etc. reach the water bodies through runoff and surface leaching during the rainy season.
Huge amount of sediments caused by accelerated rate of soil erosion (such as deforestation) reaching the rivers is a major cause of nonpoint pollution.
Examples of River Water Pollution in India
Case Study: Ulsoor Lake Pollution
Polluted by a vast floating layer of non-recycled debris comprising plastic bags and water bottles and even sacks. It witnesses frequent foaming on the surface.
Lake Water Pollution- Causes behind it
The causes of lake water pollution are similar to the river water pollution. However, the consequences in the lake water pollution is more severe as the water is stagnant unlike river water.
Siltation of lakes due to dumping of enormous quantities of sediments due to accelerated rate of soil erosion.
Toxic effluents from the urban areas.
Washing and dumping of tailings or waste sludges from factories into stagnant water.
Inorganic nutrients from agricultural fields.
Acid rain: they are often called as‘Lake Killers’.
Case Study: Bellandur Lake Pollution in Bengaluru
It has become more or less a sewage tank because of untreated sewage water entering into the lake through various inlets. In theory, clean rainwater from Koramangala and Challaghatta (K&C) Valley should flow to Bellandur lake through stormwater drains. However, Bellandur lake gets sewage inflow due to two reasons.
Improper sewage system due to which untreated sewage water overflows and joins stormwater drains, mixes with rainwater, which in turn flows to Bellandur Lake via Koramangala and Challaghatta Valley.
Lack of effluent treatment plants to treat industrial wastes from small factories that also get into the stormwater drains.
Fire at the lake: The cooking oil thrown from households that enters the lake from untreated domestic sewage is said to be the cause behind the fire.
Measures Needed for urgent restoration and remedial actions for Lake Pollution in the form of:
Desiltation of the lake is to eliminate contaminants.
Stop all encroachments of the lake with suitable fencing
Only stormwater should be allowed into the lake
Army units should discontinue effluents from cattle house wash, cow dung wash, and army mess wash and consider the installation of a biogas plant.
Plastic bags to be prevented from draining into the lake
Sewage/manholes at identified locations to be closed.
Drain water from slum around the lake to be treated before draining into the lake. Preferably, connect the slum stormwater and wastewater drain to the nearby Cox Town sewage drain as it is close to the slums
Prohibit submergence of idols during the festival season
Remove all slum dwellers from the region.
Cultivate and harvest fish and aquatic plants to deplete the nitrogen and phosphate content