NCERT Exemplar solutions for Science [English] Class 7 chapter 18 - Wastewater Story [Latest edition]

Which of the following is wastewater?

Sewage is mainly a

Which of the following is/are products of wastewater treatment?

An open-drain system is a breeding place for which of the following

Water polluted by various human activities causes a number of water-borne diseases. Which of the following is not a waterborne disease?

Pick from the following one chemical used to disinfect water.

The system of a network of pipes used for taking away wastewater from homes or public buildings to the treatment plant is known as

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

In a filtration, plant water is filtered using layers of

Which of the following is not a source of wastewater?

Why are open drains a concern?

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Sewage is a solid waste that causes water pollution and soil pollution.

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Used water is wastewater

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Wastewater could be reused.

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Where underground sewerage systems and refuse disposal systems are not available, the high-cost on-site sanitation system can be adopted.

How are open drains harmful to human health?

Name two inorganic impurities present in sewage

Animal waste, oil and urea are some of the organic impurities present in sewage. Name two more organic impurities present in sewage

Name two alternative arrangements for sewage disposal where there is no sewerage system.

A man travelling on a train threw an empty packet of food on the platform. Do you think this is a proper waste disposal method? Elaborate.

Why should we not throw used tea leaves into the sink?

Why should we not throw cooking oil and fats down the drain?

Match the items of Column I with the items of Column II with reference to sewage.

Given below is a jumbled sequence of the processes involved in a wastewater treatment plant. Arrange them in their correct sequence.

(a) Sludge is scraped out and the skimmer removes the floating grease. 

(b) Water is made to settle in a large tank with a slope in the middle.

(c) Large objects like plastic bags are removed by passing wastewater through bar screens.

(d) Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater.

(e) Wastewater enters a grit and sand removal tank.

Three statements are provided here which define the terms 

(a) sludge

(b) sewage and

(c) wastewater.

Pick out the correct definition for each of these terms.

(a) The settled solids are removed in wastewater treatment with a scraper.

(b) Water from the kitchen is used for washing dishes.

(c) Wastewater is released from homes, industries, hospitals and other public buildings.

A mixture (x) in water contains suspended solids, organic impurities, inorganic impurities (a), nutrients (b), disease-causing bacteria and other microbes. Give names for (x), (a) and (b)?

What are the different types of inorganic and organic impurities generally present in sewage?

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

Fill in the blanks in the following statements using words given in the box.

air, handpumps, cholera, water, large, ground

A very _________ number of our people defecate in the open. It may cause _________ pollution and soil pollution. Both the surface water and _________ water get polluted. _________ water is the source for wells, tubewells and _________. Thus it becomes the most common route for _________ borne diseases like _________, dysentery, etc.

Describe various steps of cleaning wastewater in a wastewater treatment plant.

Think and suggest some ways to minimise waste and pollutants at their source, taking your home as an example.