NCERT Class VII Science Solutions: Chapter 18-Wastewater Story Part 2 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Question 8:

Which of the following is a part of inorganic impurities of the sewage?

  1. Pesticides
  2. Orca
  3. Phosphates
  4. Vegetable waste

Answer: C

Question 9:

In a filtration plant water is filtered using layers of

  1. Sand and clay.
  2. Clay and fine gravel.
  3. Sand and fine gravel.
  4. Sand, fine gravel and medium gravel.

Answer: D

Question 10:

Which of the following is not a source of waste water?

  1. Sewers
  2. Homes
  3. Industries
  4. Hospitals

Answer: A

Sewers

VERY SHORT ANSWER QUESTIONS

Question 11:

Why are open drains a concern?

Answer:

It is so because they create unsanitary and unhygienic conditions.

Question 12:

State whether the following statements are true or false. In case a statement is false, write the correct statement.

  1. Sewage is a solid waste which causes water pollution and soil pollution.
  2. Used water is wastewater.
  3. Wastewater could be reused.
  4. Where underground sewerage systems and refuse disposal systems are not available, the high cost on-site sanitation system can be adopted.

Answer:

  1. Sewage is a solid waste which causes water pollution and soil pollution. (False)

(Hint: Write ‘liquid’ in place of ‘solid’ )

  1. Used water is wastewater. (True)
  2. Wastewater could be reused. (True)
  3. Where underground sewerage systems and refuse disposal systems are not available, the high cost on-site sanitation system can be adopted. (False)

(Hint: Write ‘low’ in place of ‘high’ )

Question 13:

How are open drains harmful for human health?

Answer:

Open drain system creates the most unhygienic and unsanitary condition in its neighborhood. Open dirty water drains are breeding places for flies, mosquitoes and other diseases causing organism.