Industrial pollution and its control

Detail

Why industry pollutes

• Industrial pollution: harmful matter, heat or noise that factories release into the air, water and land.
• Industry brings jobs and growth. It also harms four parts of the environment: air, water, land and noise.
• Thermal power plants (plants that burn coal, oil or gas to make electricity) are among the biggest polluters.
• Pollution is worst where many units sit close together, in industrial clusters. Examples are the chemical belt of south Gujarat and the coal-and-power belt of Singrauli.

Air pollution

• Main pollutants:
• Sulphur dioxide (SO₂): comes from burning coal and oil that contain sulphur. It turns into acid rain.
• Carbon monoxide (CO): a poisonous gas from fuel that does not burn fully.

• Particulates: tiny solid and liquid bits (dust, smoke) that hang in the air.

• Sources: chemical and paper factories, brick kilns, refineries, smelters (plants that melt ore to get metal) and any burning of fossil fuels.

• Effects: it harms people, animals, plants and buildings, and the wider environment.
• Toxic gas leaks: a sudden leak can kill many people within hours.
• Bhopal gas tragedy (December 1984), Madhya Pradesh: methyl isocyanate (MIC) gas leaked from the Union Carbide pesticide plant. It is the world's worst industrial disaster.

Water pollution

• Cause: factories release effluents (liquid waste) into rivers and lakes. Some of this waste is organic and some is inorganic.
• Main polluting industries and what they release:

Industry	Main pollutants released
Paper and pulp	Organic waste, chemicals
Chemicals	Acids, salts
Textiles and dyeing	Dyes, salts
Petroleum refineries	Oil, chemicals
Tanneries (leather)	Salts, chemicals
Electroplating	Heavy metals such as lead and mercury

• Other water pollutants: fly ash, phosphogypsum and iron and steel slag (see below).
• Heavy metals (lead, mercury) do not break down. They build up in fish and in the people who eat the fish.

Thermal pollution

• Thermal pollution: hot water from factories and power plants is drained into rivers and ponds before it cools.
• Chain of harm:
• hot water enters a river or pond → the water gets warmer
• warm water holds less dissolved oxygen (oxygen mixed into water, which fish breathe)

• fish and other water life become stressed or die.

• Nuclear waste: wastes from nuclear power plants, nuclear weapons factories and imaging equipment can cause cancers and birth defects.

Land (soil) pollution

• Cause: factories dump waste such as glass, harmful chemicals, industrial effluents, packaging, salts and garbage.
• Process:
• waste is dumped on land → rain dissolves its pollutants
• the pollutants leach (seep down) through the soil
• groundwater becomes polluted. Polluted water can also pollute the soil it flows over.

Major industrial solid wastes

Waste	Where it comes from	How it can be reused
Fly ash	Fine ash left after coal burns in thermal power plants	Bricks, cement, roads, mine filling
Phosphogypsum	Waste from making phosphoric acid in phosphate fertiliser plants	Cement, gypsum boards, soil improvement
Iron and steel slag	Stony waste left when iron and steel are made	Cement, road building

Noise pollution

• Sources: factory machines, generators, saws, electric drills, and pneumatic drills (drills worked by compressed air).
• Effects: irritation and anger, hearing loss, a faster heart rate and higher blood pressure.

Control of water pollution

• Key fact (NCERT): each litre of industrial waste water pollutes about eight times as much freshwater.
• Remedies:
• Use less water by reusing and recycling it in two or more stages.
• Harvest rainwater to meet water needs.
• Regulate how much groundwater industries draw, especially where groundwater is scarce.

• Treat hot water and effluents before releasing them into rivers and ponds.

• Effluent treatment in three stages:

Stage	Type	What happens
Primary	Mechanical	Screening (removing large solids), grinding, flocculation (making small particles clump into bigger flakes), sedimentation (letting the clumps settle out)
Secondary	Biological	Microbes eat and break down the dissolved organic waste
Tertiary	Biological, chemical and physical	Final cleaning so the waste water can be recycled

Control of air pollution

• Electrostatic precipitator (ESP): a device fitted to smokestacks that removes dust from flue gas (the smoke and gas leaving a chimney).
• flue gas passes between electrodes → the dust picks up an electric charge
• charged dust sticks to oppositely charged collecting plates

• the plates are shaken, and the dust falls into hoppers for disposal.

• Other devices used alongside it:

• Fabric filters (bag filters): cloth bags that trap dust.
• Scrubbers: spray liquid that washes out dust and gases such as SO₂.

• Inertial separators (such as cyclones): spin the gas so heavy dust is thrown out.

• Cleaner fuel: factories can switch from coal to oil or gas to cut smoke.

Control of noise pollution

• Fit silencers on machines and generators.
• Redesign machinery to make it quieter and use less energy.
• Use sound-absorbing materials.
• Workers wear ear plugs and earphones.

NTPC: an example of pollution control

• NTPC (National Thermal Power Corporation, set up in 1975) is India's largest power generator.
• It holds ISO 14001 certification. This is the international standard for an Environmental Management System (a planned way to measure and cut pollution).
• Main methods:
• It uses the latest technology and upgrades old equipment.
• It makes the most of ash utilisation.
• It plants green belts (rows of trees around plants) to protect nature.
• It runs ash ponds and ash-water recycling to cut pollution.

• It audits the environment and ecology of its plants and the land around them.

• Ramagundam (Peddapalli district, Telangana, on the Godavari river): an NTPC super thermal plant used as an example of these methods.

Fly ash rules (2021)

• Fly ash: the fine, powdery ash left after coal is burnt in a power plant. It blows into the air, it is dumped in ash ponds that take up farmland, and it pollutes water.
• The 2021 ash utilisation rules of the Ministry of Environment, Forest and Climate Change require 100% use of the ash from coal and lignite power plants.
• Permitted uses: fly ash bricks, cement, road and flyover embankments, and filling old mines.

Comprehensive Environmental Pollution Index (CEPI)

• CEPI: a score from 0 to 100 made by the Central Pollution Control Board (CPCB). It measures how polluted the air, water and land of an industrial cluster are. A higher score means worse pollution.
• First assessment (2009):
• 88 industrial clusters were studied with the Ministry of Environment [2].
• 43 clusters in 17 states were called Critically Polluted Areas (CEPI 70 or more) [2].

• 32 clusters were called Severely Polluted Areas (CEPI 60–70) [2].

• Top of the list: Ankleshwar (Bharuch district, on the south bank of the Narmada) and Vapi (Valsad district, south Gujarat, near Daman). Both are chemical and dye hubs.

• Other critically polluted clusters: Ghaziabad (Uttar Pradesh, National Capital Region) and Singrauli (on the Madhya Pradesh–Uttar Pradesh border, a hub of coal mines and thermal power plants).
• Result: the government stopped approving new units in these clusters for a time (a moratorium) until cleanup action plans were in place.
• Later rounds: clusters were scored again in 2011 and 2013 [2].
• Revised directions (26 April 2016): all Critically Polluted Areas must have continuous air-quality and water-quality monitoring stations. A revised CEPI method must be used, with results checked by independent laboratories and made public [2].

Newer tools

• Online Continuous Emission/Effluent Monitoring Systems (OCEMS): sensors in chimneys and drains send pollution data live, all the time.
• On 5 February 2014, CPCB used Section 18(1)(b) of the Water Act (1974) and Air Act (1981) to order OCEMS in the 17 categories of highly polluting industries [3].

• The 17 categories: pulp and paper, distillery, sugar, tanneries, power plants, iron and steel, cement, oil refineries, fertiliser, chlor-alkali, dye and dye intermediates, pesticides, zinc, copper, aluminium, petrochemicals and pharmaceuticals [3].

• Zero Liquid Discharge (ZLD): a factory treats and reuses all its waste water, so no liquid leaves the plant.

• Polluter pays principle: whoever causes the pollution pays to clean it up and to compensate the people harmed.

Prelims Hooks

• Under NCERT, each litre of industrial waste water pollutes about eight times as much freshwater.
• Primary treatment is mechanical (screening, grinding, flocculation, sedimentation). Secondary treatment is biological. Tertiary treatment is biological, chemical and physical. Trap: flocculation is a primary step, not a secondary one.
• An electrostatic precipitator removes particulates (dust), not gases. Scrubbers remove gases such as SO₂.
• Fly ash comes from thermal power plants. Phosphogypsum comes from fertiliser plants. Slag comes from iron and steel plants.
• NTPC was set up in 1975. It holds ISO 14001 (Environmental Management System). Its model plant is Ramagundam, Telangana.
• CEPI (2009): 88 clusters were assessed and 43 were critically polluted (score of 70 or more) [2]. Ankleshwar and Vapi (Gujarat) topped the list.
• Singrauli sits on the Madhya Pradesh–Uttar Pradesh border. It is a coal and thermal power cluster.
• Bhopal (1984): methyl isocyanate leaked from the Union Carbide plant.
• CPCB's OCEMS order of 2014 covers 17 categories of highly polluting industries [3].

Mains Points

• Clusters concentrate pollution:
• industries gather near raw materials, ports and markets (Ankleshwar–Vapi, Singrauli, Ghaziabad)
• their waste piles up in the same rivers, air and land

• the result is "critically polluted" zones and moratoria on new units, which force a trade-off between growth and environment (GS-III).

• The coal-power burden: thermal plants produce fly ash, SO₂ and hot water. The answer is a set of tools: ESPs, scrubbers, 100% fly ash use (2021) and NTPC-style green belts and ash-water recycling.

• Water stress and effluents: one litre of waste water pollutes about eight litres of freshwater. Three-stage treatment, ZLD, rainwater harvesting and limits on groundwater use are therefore key to industrial water security.
• From rules to monitoring: CEPI scoring, live OCEMS data from the 17 polluting categories [3], continuous monitoring stations (2016) [2] and the polluter pays principle shift control from one-time permits to constant checks.