Sources of water pollution - class-X

Thermal pollution, caused by the discharge of heated water from power plants or industries into water bodies, significantly alters aquatic ecosystems and harms aquatic life.

Thermal pollution is defined as the degradation of water quality by any process that changes ambient water temperature, typically through the use of water as a coolant by power plants.

The presence of nitrogen in sewage, often in the form of proteins or urea, is a primary indicator of organic matter content.

Chemical Oxygen Demand (COD) is a measure of the amount of oxygen required to chemically oxidize organic compounds in water, commonly used to assess the strength of sewage.

Water pollution is considered a critical hazard because water is essential for all life forms, and its contamination directly impacts human health and global ecosystems.

Mining, agro-industries, and thermal power plants all contribute significantly to water and soil pollution through chemical runoff, heavy metals, and thermal discharge.

Nuclear power plants use water for cooling purposes. The discharge of this water back into the environment at elevated temperatures causes thermal pollution.

Sewage contains the highest amount of carbonic materials and biological materials as pollutants. It increases the number of decomposers like bacteria and fungus. The acceleration of microbial activity increases BOD of water.

The foul odor and taste of the drinking water is due to geosmin and methylisoborneol that are organic compounds produced by blue-green algae. Thus the correct answer is option D.

Water pollution is the major cause of several chronic diseases. The potable water must be treated to get rid of certain harmful microorganism. Daphnia, trout fishes, and larvae of stone flies are the example of fresh water indicator and tubifex, E. Coli, sewage fungus, sludge worms, blood worms are the indicator of polluted water.

Addition of undesirable substances to water and removal of desirable substances from it is termed as water pollution. But the addition of harmful substances causes a very harmful effect leading to water pollution. For example, the addition of industrial smoke, effluents, washing dirty clothes, bathing, sewage waste, etc causes water pollution.

Water pollution is the major cause of several chronic diseases. The potable water must be treated to get rid of certain harmful microorganism. Daphnia, trout fishes, and larvae of stoneflies are the example of freshwater indicator and tubifex, E. Coli, sewage fungus, sludge worms, blood worms are the indicator of polluted water.

Stone fly larvae are highly sensitive to water pollution and require high levels of dissolved oxygen, making them indicators of clean, unpolluted water.

Coal-based power plants require massive amounts of water for cooling, which is then discharged at a higher temperature, leading to significant thermal pollution in nearby water bodies.

The biodegradable substances can be degraded with the decomposition activity of the microbes. The cow dung is the pollutant which is the waste produced by the animals like cattle. The cow dung mainly contains the cellulosic fibres. This is a biodegradable form of pollutant which can be decomposed by the enzyme cellulase produced by the microbes. DDT is a pesticide, the lead vapour is produced due to combustion of leaded fuels and plastic is a synthetic polymer. These materials cannot be degraded.

Phosphates are used to manufacture Detergents.

Thermal pollution refers to effluents and hot water from thermal plants or atomic reactors which bring about the rise in water temperature. Warm water contains less oxygen, resulting in increased organic loading, and replacement of green algae by blue-green algae.

• There are wastes that are generated on an everyday level, classified as non-biodegradable wastes because they cannot be degraded by microbial activity.
• These wastes cannot be burned because they release harmful gases and result in air pollution. 
• Dumping and burying of this wastes may cause leaching of the chemicals which causes soil pollution. 
• Recycling is the best way to manage these waste forms. 
• Recycling will help in the reduction of the wastes and the waste will be transformed into useful forms.
• Thus, the correct answer is option D. 

Conserving water in industry involves a multi-faceted approach, including wastewater treatment, recycling (often via reverse osmosis), and regular maintenance to prevent leaks.

About 71% of the Earth's surface is covered by water. There is only 3% of water which is considered as pure or fresh water. This water is present in lakes and rivers. This pure water is used for various different activities. It is also known as potable water. About 5-10% of pure water is used for the industrial purposes.

Industrial effluents are the major water pollutants because of their ingredients. Heavy metal waste like mercury, cadmium, dirt and gravel, masonry and concrete, scrap metal, trash, oil, solvents and chemicals etc. are present in the industrial effluents. Their treatment is a long and expensive procedure as compared to domestic sewage treatment. The industrial waste is corrosive, reactive and igniting. It poses dangerous effects on the aquatic life primarily and human health thereafter. These have shown the biomagnification capability as well.

• Suspended solids in water refer to various impurities like sand, slit, small stones, etc. These are heavy ad get submerged at the bottom of water. They do not easily mix or dissolved easily with water. So, they can be separated from water by various means like sedimentation, water filter, etc. 
• Bacteria are very minute organisms that are not even visible to naked eyes and thus their removal becomes very difficult. Proper disinfection is required to remove them. 
• Colloids and other suspended impurities also need special filtration and purification techniques to be separated from the water.
• So, option D is the correct answer.

Agricultural discharge such as large quantity of agrochemicals, organic matter, sediments and saline drainage, fertilizer extract directly released in water bodies contaminate water and cause waterlogging. Sewage and untreated waste containing the high amount of organic compound and industrial effluent including organic, non-organic and reactive waste released in water have the potential to acidify water bodies, the solid waste accumulation can result in drying up of waters.

Escherichia coli is a coliform bacterium commonly found in the lower intestine of warm-blooded organisms. Its presence in water samples serves as the standard indicator organism for fecal contamination and water pollution.

Oxygen is less soluble in warm water. Hence, as the water temperature increases the dissolved oxygen decreases.

Cadmium (Cd) is one of the most toxic elements to which humans could be exposed at work or in the environment. The outbreak of itai-itai disease, which is the most severe stage of chronic Cd poisoning, occurred in the Cd-polluted Jinzu River basin in Toyama.

Iron is particularly problematic in paper manufacturing because it causes staining and discoloration of the paper product.

Detergents that are released from the domestic sewage, as well as the industrial effluents, are the causative pollutants because these result in the increasing the inorganic mineral quantity in the water body. Because of this, the eutrophication occurs. The dissolved oxygen in the water body is decreased and the aquatic life suffers from the hypoxia. Plastic, glass junk and iron junk persist in nature as they are non-biodegradable. Their downhill causes are less as compared to the detergents.

Detergents are the chemicals that have an efficient cleaning ability due to the surfactants present in them. In order to provide the whitening effect, detergent contains bleach. Their are optical brightening substances called fluorescers also present. The perborates are added in the detergents as they provide effective oxidizing property. However, all these chemical are nondegradable in natue and tend to persist in the environment. Hence, the correct answer is ‘All of the above’.

Thermal pollution refers to the water pollution caused by the discharge of the hot industrial effluent in the water body that destroys the ambient temperature of the water body. The thermal pollution is a major water pollution near the coal power plants that use water as the coolant so that it absorbs the thermal energy from the thermal plants and then the hot water is released in the nearby water body. The rise in temperature of the water causes severe adverse effects to the aquatic life.

The eco-friendly detergents are free from the added chemicals, instead they have enzymes to catalyse the reactions. They do not contain phosphates, bleaches, synthetic perfumes, brightening chemicals etc. They contain lipases and proteases that break down the fats and proteins, so they are effective in stain removal. Hence, the correct answer is 'Phosphates and bleaches'.