Question

Which of the following industries are responsible for water pollution?
A. Oil refineries
B. Paper factories
C. Textile and sugar mills
D. Chemical factories

Answer 1

Human beings are damaging and abusing the water bodies . They dispose of all the waste material into water bodies polluting the water. Realizing the importance of maintaining the cleanliness of the water bodies, the government of India has passed the water (prevention and control of pollution) act 1974 to prevent water resources.

Step by step answer: Unlike domestic sewage, wastewater from industries like petroleum, paper manufacturing. metal extraction and processing, chemical manufacturing, etc., often contain toxic substances, notably, heavy metals (defined as elements with density $\mathop { > 5g/cm}\nolimits^3$such as mercury, cadmium, copper, lead. etc.) and a variety of organic compounds. So, they cause water pollution.
Option A - Oil refineries:- Many industries, including power plants and oil refineries, use water as coolant for the machinery. Release of hot wastewater, having 8 to 10°C higher temperature than the intake water, causes thermal pollution in the water body and also reduces dissolved oxygen.
Option B - Paper factories:- The waste generated from paper has low oxygen. So they high BOD. Thereby they pollute water bodies. They cause aquatic organisms to die because of the low oxygen present in this waste.
Option C - Textile and sugar mills:- the effluents are released from sugar and textile factories and damages the water. This waste contains some amount of chemicals that cause the aquatic organism to die and thus causes water pollution.
Option D - Chemical factories:- Insecticides and Pesticides are used in agriculture which when released in water bodies causes water pollution. They reduce the amount of dissolved oxygen in water bodies causing the death of aquatic organisms.
Hence, the option are oil refineries, paper factories, textile and sugar mills, and chemical factories.

Note: Insecticides are biologically active chemicals used for pest control. These include D.D.T., B.H.C., copper sulphate, and aldrin, etc. Aquatic microorganisms absorb them in fats and oils. Fish feeding on these zooplanktons and phytoplanktons further concentrate these pesticides in their tissues. Birds feeding on these fish concentrate these pesticides still more. The increased accumulation of these toxic substances in the food chain at a higher trophic level is called biological magnification.