Treatment of waste material, Use of high chimney, using electrostatic precipitator to remove particulate matter, use scrubber to remove harmful gases like SO₂.

Events that reduce biological oxygen demand of primary effluent.
The amount of oxygen required for microbial breakdown of biodegradable organic matter is called BOD. It is higher in polluted water and lesser in drinking water. Primary treatment is physical treatment. The supernation of settling tank is called effluent.  It is put into biological treatment involving microbial decomposition fine organic matter. It is further heated by trickling filter and activated sludge method.

Water pollution from surface run off:
Pollutants in surface run off (and storm water) vary according to the nature of land over which it flows. The run off from agricultural land is contaminated with pesticide residues and residues of inorganic fertilzers. The run off from urban areas mainly contains biodegradable organic pollutants. Industrial sites may contribute to varied types of pollutants like heavy metals, acids and various inorganic compounds. All these pollutants in the run off heavily contaminate our surface water and groundwater resources.

The Central Pollution Control Board has recommended the zone-wise ambient noise levels.
 Zone-wise Permissible Ambient Noise Levels

Acid rains: Sulphur dioxide and sulphur trioxide are produced by oxidation of sulphur in the fossil fuels. These gases react with water and form sulphuric acid or sulphurous acids. These acids when precipitated as rain or snow create acid rain or acid precipitation. The pH of acid rains is less than 5-6 as could be as low as 4. Acid rain adversely affect plant vegetation by causing chlorosis and necrosis.

(i) Photochemical Smog: It is secondary pollutant. It is yellowish brown smog which is formed under oxidising conditions and high temperature over cities and towns that are releasing a lot of nitrogen oxides and unburnt hydrocarbons. In still air the two interact photochemically to produce photochemical oxidants-ozone, PAN, aldehydes and phenols. Photochemical smog does not have any appreciable amount of primary pollutants. It is also called Los Angeles.

1. Only 51% of solar energy reaches the earth surface.
2. It is because it is absorbed by the gases and molecules in the atmosphere.

E- wastes are recycled in the developing countries, as they recover some costly elements like copper,gold, nickel,silicon, etc.
Recycling in developing countries involves manual participation and workers are exposed to the toxic substances and get certain respiratory diseases.

(a) Carbon dioxide, Methane, Chlorofluoro carbons and nitrous oxide.
(b) Chlorofluorocarbons cause ozone hole.
(i) In the stratosphere chlorofluorocarbon is degraded in the presence of UV-radiation, releasing CI atoms.
(ii) CI acts as catalyst in the degradation of ozone releasing molecular oxygen; since CI atoms are not used up in the reaction, they continue to affect the ozone levels.

The smoke stacks of thermal power plants release particulate and gaseous air pollutants.
1. These pollutants when inhaled deep into the lungs can cause:
(i) breathing or respiratory disorders.
(ii) irritation, inflammations and damage to lung alveoli and
(iii) premature death.
Control measure
By use of electrostatic precipatores,99% of the particulate matter can be removed.

1. The CFCs discharged in the lower part of atmosphere move upward and reach the stratosphere.
2. In the stratosphere, UV rays act on them releasing Cl atoms.
3. Cl acts as a catalyst and degrades ozone releasing molecular oxigen
4. Since Cl atoms are not consumed in the reaction, whatever CFCs are added to the stratosphere, continue to damage the ozone and cause ozone depletion.
5. So, the emission of CFCs must be reduced.

1. The CFCs discharged in the lower part of atmosphere move upward and reach the stratosphere.
2. In the stratosphere, UV rays act on them releasing Cl atoms.
3. Cl acts as a catalyst and degrades ozone releasing molecular oxigen
4. Since Cl atoms are not consumed in the reaction, whatever CFCs are added to the stratosphere, continue to damage the ozone and cause ozone depletion.
5. So, the emission of CFCs must be reduced.

(i) Irreparable computers and (ii) other electronic gadgets.
(i) Incineration and (ii) burying in the landfills.
(a) In developing countries, they are recycled involving manual labourers.
(b) In developed countries, they are recycled in specifically built chambers, without involving manual labourers.

(i) Irreparable computers and (ii) other electronic gadgets.
(i) Incineration and (ii) burying in the landfills.
(a) In developing countries, they are recycled involving manual labourers.
(b) In developed countries, they are recycled in specifically built chambers, without involving manual labourers.