(a) How do industries increase air pollution? Suggest any three measures to reduce air pollution.

Role of industries in increasing air pollution-

(i) Air pollution is caused by the presence of high proportion of undesirable gases, such as sulphur dioxide and carbon monoxide.

(ii) Airborne particulate materials contain both solid and liquid particles like dust, sprays mist and smoke.

(iii) Smoke is emitted by chemical and paper factories, brick kilns, refineries and smelting plants, and burning of fossil fuels in big and small factories that ignore pollution norms.

(iv) Toxic gas leaks can be very hazardous with long-term effects.

Suggestions to control air pollution-

(i) Particulate matter in the air can be reduced by fitting smoke stacks to factories with-

a. electrostatic precipitators,

b. fabric filters,

c. scrubbers

d. inertial separators.

(ii) Smoke can be reduced by using oil or gas instead of coal in factories.

(iii) Increasing the height of chimneys.

(iv) Shift to renewable energy sources.

(b) How do industries increase thermal pollution? Suggest any three measures to reduce thermal pollution.

(i) Thermal pollution of water occurs when hot water from factories and thermal plants is drained into rivers and ponds before cooling.

(ii) Wastes from nuclear power plants,

Measures to reduce thermal pollution-

(i) Treating hot water and effluents before releasing them in rivers and ponds. Treatment of industrial effluents can be done in three phases.

(ii) Primary treatment by mechanical means. This involves screening, grinding, flocculation and sedimentation.

(iii) Secondary treatment by biological process

(iv) Tertiary treatment by biological, chemical and physical processes. This involves recycling of wastewater.