BOD is the amount of oxygen required by bacteria to break down organic materials present in water.
Why does water covered with excessive algai growth become polluted.

BOD is the amount of oxygen required by bacteria to break down organic materials present in water. What is the importance of measuring BOD of a water body?

Break down of complex organic matter into inorganic raw material like CO_2 , water and various nutrient by micro organism _____

Ozone is an allotrope of oxygen. The ozone layer present at the upper part of the atmosphere protects the earth’s surface from excess UV radiation. Why does black lead sulphide become white, on treating with ozone?

Read the following passage and answer the questions given. The production and improper disposal of waste are causes for a great deal of environmental pollution. Many toxic industrial wastes from manufacturing process require treatment and /or safe disposal. When materials are recycled, apart from saving on the coast of raw material, waste disposal coast are reduced. Some combustible materials like dried leaves etc can be burnt to get heat energy. Sewage treatment includes filtering, scudge settlement, degradation coagulation disinfection using chlorine etc. Certain microorganisms can degrade waste in the absence of oxygen-digestion. Sewage water is purified by: light, Fishes, Microorganisms, Aquatic plants