Read the extract given below and answer any 5 out of 6 questions:
Every litre of waste water discharged by our industry pollutes eight times the quantity of fresh water. How can the industrial pollution of fresh water be reduced? Some suggestions are-
(i) Minimising the use of water for processing by reusing and recycling it in two or more successive stages.
(ii) Harvesting of rainwater to meet water requirements.
(iii) Treating hot water and effluents before releasing them in rivers and ponds. Treatment of industrial effluents can be done in three phases.
(a) Primary treatment by mechanical means involves screening, grinding, flocculation and sedimentation.
(b) Secondary treatment is by biological process.
(c) Tertiary treatment by biological, chemical and physical processes. This involves recycling of waste water.
Overdrawing of ground water reserves by industry where there is a threat to ground water resources also needs to be regulated legally. Particulate matter in the air can be reduced by fitting smoke stacks to factories with electrostatic precipitators, fabric filters, scrubbers and inertial separators. Smoke can be reduced by using oil or gas instead of coal in factories. Machinery and equipment can be used and generators should be fitted with silencers. Almost all machinery can be redesigned to increase energy efficiency and reduce noise. Noise absorbing material may be used apart from personal use of earplugs and earphones. The challenge of sustainable development requires integration of economic development with environmental concerns.
How many treatments are there for industrial effluents?