Effects of Domestic Sewage and Industrial Effluents on Water

Water samples were collected at points A, B and C in a segment of a river near a sugar factory and tested for BOD level. The BOD levels of samples A, B and C were 400 mg/L, 480 mg/L and 8 mg/L respectively. What is this indicative of? Explain why the BOD level gets reduced considerably at the collection point C?

Observe figure and answer the following questions.

Biomagnification of DDT in an aquatic food chain

1. What ecological term is used to describe the DDT accumulation at different trophic levels?
2. List any one effect of DDT accumulation on birds
3. Will DDT accumulation lead to eutrophication?
4. Does it affect the BOD?
5. Name disease caused by accumulation of any heavy metal.

What are the three major kinds of impurities in domestic wastewater?

What do you understand by biomagnification?

Algal bloom results in ______.

How has DDT caused decline in bird population?

Public all over India is very much concerned about the deteriorating air quality in large parts of North India. Alarmed by this situation the Resident's Welfare Association of your locality organized an awareness programme entitled "Bury not burn". They invited you, being a biology student to participate.

(a) How would you justify your arguments that promote burying and discourage burning? (Give two reasons)

(b) With the help of flow charts, one for each practice depict the chain of events that follow.

A high Biological oxygen demand (BOD) indicates that ______.