NCERT Exemplar Class 7 Science Chapter 18 Solutions: Wastewater Story

NCERT Exemplar Class 7 Science Solutions Chapter 18 Wastewater Story have been prepared to assist you through the exemplar problems. In this chapter of NCERT Exemplar Class 7 Science Solutions, you will learn about sewage, International Decade for action on “Water for life”, the process of cleaning of water, treatment of polluted water, wastewater treatment plant, better housekeeping practices, Sanitation and Diseases, alternate arrangement for sewage disposal and sanitation at public places.

There are a total of 27 Exemplar problems in this chapter. These questions are of a diverse variety. You will get true or false, fill in the blanks, objective and subjective questions. These questions are arranged in a fashion such that the difficulty level increases according to your compatibility. The questions will give you an idea of the questions that come frequently in the exam.

The Instasolv experts of science have kept themselves updated with the latest trends in question papers and the guidelines of the CBSE. Instasolv aims at making you aware of the topic’s demands. NCERT Exemplar Class 7 Science Chapter 18 also holds importance in your practical life, therefore it is very necessary that you use this as a source of reference for the Exemplar problems for complete clarity in the subject.

Important Topics in NCERT Exemplar Class 7 Science Solutions Chapter 18

Introduction to Wastewater:

The water that has been put to use once is known as wastewater. We can reuse the wastewater by treating the pollutants present in it by various techniques that we will learn in this chapter.

United Nations declared 2005-2015 as the International Decade for action on “Water for Life”


The used water with pollutants that come out of residents, industries, hospitals, offices, or even water runoff from streets during heavy rains is termed as sewage water. It can have both dissolved impurities as well as suspended impurities which are termed as contaminants.

The composition of sewage is a complex mixture that has suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease-causing bacteria

Treatment of Sewage

Water is carried through a network of pipelines called sewers. This network is known as sewerage. This network of pipelines carries the sewage water to the treatment plant. In a Wastewater Treatment Plant (WWTP), the following steps are followed:

  1. Wastewater is made to go through bar screens where large impurities are filtered.
  2. Now, the water goes to the grit and sand removal tank. With the speed of the water decreased the suspended particles such as sand, grit and pebbles settle down here.
  3. The solids such as faecal matter settle down as sludge which is removed by a scraper while a skimmer removes the greasy floatable solids.
  4. Biogas is produced in a separate tank by decomposition of sludge by anaerobic bacteria.
  5. Air is pumped into the clean water to help aerobic bacteria clean the human, food and other wastes remaining in the water.

Better House Keeping Practices: such as not throwing cooking oil and fats in drains, also preventing chemical wastes from draining, throwing solid food wastes in dustbin helps in making the water treatment easier as well as better quality-wise.

Poor Sanitation: can cause a large number of fatal diseases.

These days onsite sewage disposal systems are being tried upon. 

We should follow hygienic public sanitation practices to prevent everyone from diseases caused by poor sanitation.

Exercise Discussion of the NCERT Exemplar Class 7 Science Solutions Chapter 18

  1. The NCERT Exemplar Class 7 Solutions problems from 1 to 10 are multiple-choice questions which will help you in test your knowledge thoroughly on waterborne diseases, how to disinfect water, inorganic impurities in water, filtration etc. 
  2. The exercises 11 to 13 are consist of very short one-word answer type questions which will help you quickly revise all the topics of the chapter.
  3. The short answer type questions from 14 to 22 are very engaging. They include topics like sewage disposal, inorganic impurities in water, wastewater treatment etc.  
  4. The long answer type questions in the exemplar exercise are analytical and practical on the treatment of wastewater, how to minimize water pollution etc.

Why Use NCERT Science Exemplar Solutions Class 7 Chapter 18 by Instasolv?

The NCERT Exemplar problems solutions of chapter 18 are prepared by the science faculty of Instasolv in a layman’s language to help you quickly memorise the important questions. Using Instasolv as the source of reference for your exemplar exercises, you will find a substantial boost in your marks. All the Exemplar answers are stepwise and include clear explanations. They will help you understand the chapter and practice its tough topics easily.