18. Wastewater Story Science class 7 in English Medium ncert book solutions topic -4

Additional Question with solution:

Que:  World water Day is celebrated on.

Ans:  22 March.

Que: Mention the period proclaimed as the International Decade for action on water for life.

Ans: 2005 - 2015 is the period proclaimed as the international Decade for action on water for life. 

Que: Name the three processes involved in treatment of wastewater.

Ans: Treatment of watewater involves physical, chemical and biological processes for removing different types of contaminants.

Que: Explain sewers and sewage.

Ans: Sewers are the pipes acting as a transport system that carries sewage from point of origin to the point of disposal. The wastewater released from homes, industries, hospitals, offices and other uses is called swewge.

Que: The used water should not be wasted. Do you agree? Justify.

Ans: The used water should not be wasted but it should be cleaned.

Que:  Bleaching powedr is mixed in water, why? Think and give appropriate reson for it.

Ans: Bleaching powder is mixed in water to make it safe for drinking because it kills the harmful germs present in water.

Que: Natural water is the purest from of water. Explain why or why not.

Ans: Natural water is not pure always. It is because all types of water except rainwater contain salts dissolved in it. Theses salts make the water impure. 

Que:  Mention the role of effluent treatment plants in cities.

Ans: The effluent treatment plants filter out undissolved materials from water.

Que: Protozoa is causative organism of which waterborne disease?

Ans:  Dysentry.

Que: Saniation can be improved. Explain, what step should be taken to improve it. 

Ans: Low cost onsite sewage disposal system must be encouraged to improve sanitation.

Que: Give the percentage of water being activated in sludge. 

Ans: About 97% of water is being activated in sludge.

Que: Wastewater is fit for human consumption or not. give reason to support your.

Ans: No, because it is dirty and has many diseases causing organisms like cholera, typhoid, etc.

Que: Name two chemicals used to disinfect wastewater.

Ans: Chlorine and ozone.

Que: Special type to toilets has been designed in aeroplanes, name it.

Ans: Vacuum toilets.

Que: Name the toilets used in areas with limited water supply.

Ans: Vermi - processing toilets.

Que: Open drain is big concern now - a - days. Justify.

Ans: Open drain is big concern for the society now - a days because they create unhygienic conditions. It provides favourable conditions to filies, mosquitoes and unhygienic conditions. It provides favourable conditions to filies, mosquitoes and other insects to breed and spread a number of diseases.

Que: Sewage also contains some nutrients Comment.

Ans: Sewage is a complex mixture which contains suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes.

The nutrients present in sewage are phosphorus and nitrogen.

Que: The terms sewage, sewers and sewerage are interlinked with each other. Can you explain, how?

Ans: The terms like sewage, sewage and sewerage are interlinked with other because sewage is a mixture of watewater coming out of homes and other places. Sewers are pipes which carry sewage and sewerage is a network of sewage carrying pipes.