Glossary
- Water Pollution:
The alteration of water’s normal properties due to the presence of harmful foreign materials (pollutants), resulting in contamination of water bodies such as rivers, lakes, and oceans. - Water Pollutants:
Foreign substances that pollute water and may cause harm to plants, animals, and humans. Examples include industrial waste, sewage, agricultural runoff, and oil spills. - Potable Water:
Water that is safe for human consumption and does not cause any water-borne diseases. Potable water should be free from harmful chemicals, microorganisms, and impurities. - Waterborne Diseases:
Diseases caused by consuming contaminated water. These diseases include cholera, typhoid, and dysentery. - Acidity:
A measure of how acidic or alkaline water is, typically determined by the pH level. Water with a pH level below 7 is acidic, and above 7 is alkaline. - Suspended Impurities:
Tiny particles that are present in water, making it cloudy. These can be removed through various purification methods like filtration or settling. - Chlorination:
A method of purifying water by adding chlorine, which kills harmful bacteria and microorganisms, making the water safe for drinking. - Boiling:
A simple and effective method to purify water. By heating water to its boiling point, harmful germs and microorganisms are killed. - Filtration:
A physical method of purifying water, where it is passed through materials like sand, gravel, and charcoal to remove impurities. - Loading:
The process of adding alum (phitkari) to water to make suspended particles heavier, causing them to settle at the bottom. The clear water is then decanted for use. - Sewage:
Wastewater from households and industries that contains human waste, food scraps, chemicals, and other pollutants. It must be treated before being released into water bodies. - Industrial Waste:
Waste generated by factories and industries, often containing harmful chemicals that can pollute water sources. - Oil Spill:
The release of oil into the ocean or water bodies, often caused by accidents or leakage from oil tankers. It damages marine life and ecosystems. - Agricultural Runoff:
Water that carries fertilizers, pesticides, and other chemicals from farms into nearby water bodies, causing pollution. - Aquatic Life:
The organisms that live in water bodies, such as fish, plants, and microorganisms. They can be harmed by water pollution. - Algae Blooms:
The rapid growth of algae in water, often caused by excess nutrients from sewage and agricultural runoff. Algae blooms deplete oxygen in the water and harm aquatic life. - Microorganisms:
Tiny living organisms, such as bacteria and viruses, that can contaminate water and cause diseases if present in unsafe amounts. - Sterilization:
The process of killing harmful microorganisms in water to make it safe for drinking. Chlorination is one common method of sterilization. - Water Conservation:
The practice of using water efficiently and preventing its waste, ensuring that it is available for future generations. Methods include reducing water usage, reusing water, and recycling water. - 3R’s Principle:
The concept of “Reduce, Reuse, and Recycle,” which encourages the reduction of water consumption, reuse of water where possible, and recycling of water to conserve resources. - Phytoremediation:
The use of plants to remove contaminants from water bodies. Some plants can absorb pollutants like heavy metals or excess nutrients, helping to purify water. - Boiling Point:
The temperature at which a liquid changes into a gas. For water, this is 100°C (212°F) at standard atmospheric pressure. - Waterborne Pathogens:
Harmful microorganisms, such as bacteria, viruses, and protozoa, that can be transmitted through contaminated water, leading to waterborne diseases. - Alum (Phitkari):
A chemical compound used in water treatment to clarify water by causing suspended particles to clump together and settle. - Turbidity:
The cloudiness or haziness of a water sample caused by the presence of suspended particles. High turbidity can indicate pollution or the presence of microorganisms. - Water Purification:
The process of removing contaminants from water to make it suitable for consumption or other uses. This can be done through methods like filtration, boiling, chlorination, and distillation.
Something To Know
A. Fill in the blanks.
- ___________ is a chemical method of purifying water.
Answer – Chlorination
- ___________ and ___________ constitute agricultural wastes.
Answer – Fertilizers and pesticides
- The presence of domestic sewage, in water, promotes the growth of ___________ and ___________ which use up a lot of oxygen, present in water.
Answer – algae, bacteria
- Water, that is safe for drinking, is called ___________ water.
Answer – potable
- One of the purposes of purification of water is to remove the ___________ impurities, present in it.
Answer – suspended
B. State True or False for the following statements.
- A bad taste of water indicates the presence of pollutants in it.
Answer – True
- We should always bathe, and wash clothes, in rivers.
Answer – False
- Potable water can cause water borne diseases.
Answer – False
- We should always wash and clean our vehicles with tap water using a pipe.
Answer – False
- The ‘waste water’ produced by the industrial units, must be (appropriately) treated before it is discharged into rivers.
Answer – True
C. Tick (✓) the correct option.
- Domestic sewage, released into rivers, causes
growth of algae
increase in oxygen
survival of aquatic life
killing of bacteria
Answer – growth of algae
- Water, which is safe for drinking, is known as—
potable water
rain water
sea water
pond water
Answer – potable water
- One of the methods, that can help in destroying harmful germs in water, is—
filtering
chlorination
addition of fertilisers
loading
Answer – chlorination
- Suspended particles are made heavier by adding alum. This process is known as—
loading
chlorination
decantation
filteration
Answer – loading
- A method, that can help in conservation of water, is—
using shower
half flush
water dripping from leaking tap
water running for rinsing
Answer – half flush
D. Answer the following questions in brief:
- State any two ways which can lead to contamination of water.
Answer – Industrial waste disposal into water bodies.
Agricultural runoffs containing fertilizers and pesticides.
- Give the meaning of the term ‘water pollutants’.
Answer – Water pollutants are foreign substances or chemicals that contaminate water, causing it to become harmful for plants, animals, and humans.
- Name two of the main diseases that can be caused by drinking contaminated water.
Answer – Jaundice
Diarrhoea
- Name two chemicals that may help in purifying water.
Answer – Chlorine (used in chlorination)
Alum (used in the loading process)
- Name the kind of ‘growths’ in water that lead to a depletion of the oxygen dissolved in it.
Answer – Algae and bacteria
E. Answer the following questions.
- List the main parameters that need to be followed before water is supplied for drinking purposes.
Answer – Water must be colourless and free from any odor or smell.
It must be free from suspended impurities.
It should be tasteless.
It must be free from microorganisms which cause diseases.
It must be free from harmful chemicals.
- Write, in brief, (i) one physical and (ii) one chemical method that can be used for ’water purification’.
Answer – (i) Physical Method: Filtration — Water can be purified by passing it through layers of sand, gravel, and charcoal to remove physical impurities.
(ii) Chemical Method: Chlorination — Chlorine tablets or bleaching powder can be added to water to kill harmful microorganisms and make the water safe for drinking.
- State the measures that must be taken to check water pollution by sewage.
Answer – Sewage must be churned using machines, allowing heavier particles to settle.
Sewage water should be treated with chemicals like alum to purify it.
The water should be sterilized by chlorination to kill harmful microbes before being released.
- Suggest some simple steps that can be taken to help in conserving water.
Answer – Avoid using showers and opt for buckets and mugs while bathing.
Turn off the tap while brushing teeth.
Do not let water go to waste when washing dishes or cleaning.
Use a bucket for washing vehicles instead of using a hosepipe.
Repair any leaky taps to prevent water wastage.
Value Based Question
Ajay and Amit are good friends. One day when Ajay went to Amit’s home, he noticed that some of the taps, in the kitchen and bathroom were leaking. Ajay discussed this with Amit and explained to him the necessity of avoiding the wastage of water. He also talked to his father and gave Amit the mobile number of the plumber who could repair their leaking taps. Amit promised that he would request his parents to do the needful at the very earliest.
- State the values displayed by Ajay.
Answer – Ajay displayed the values of responsibility, awareness, and helpfulness. He noticed the water wastage due to leaking taps, understood its importance, and took the initiative to discuss it with his friend Amit. Additionally, he suggested a practical solution by providing Amit with the plumber’s contact, showing concern for the conservation of water.
- Suggest some simple steps, that can be taken, to avoid wastage of water?
Answer – Repair any leaking taps immediately.
Turn off the tap while brushing teeth or washing hands.
Use a bucket instead of a hosepipe for washing cars.
Collect rainwater for non-drinking purposes like gardening.
Use a water-saving showerhead to reduce water flow.
Avoid leaving the tap open when washing dishes or vegetables.
- Suggest a simple method to make an estimate of the amount of water wasted through a (slightly) leaking tap over a month. Try to find out the extent to which such ‘leaked and wasted’ water can meet the ‘daily water requirements’ of a single person.
Answer – Step 1: Measure the amount of water leaking from the tap per minute. For example, if the leak is slow and drops around 1 drop every 2 seconds, there are approximately 30 drops per minute.
Step 2: Estimate the amount of water wasted per hour:
30 drops/minute × 60 minutes = 1,800 drops per hour.
(1 drop of water = approximately 0.05 milliliters)
1,800 drops × 0.05 ml = 90 ml per hour.
Step 3: Multiply the hourly wasted water by the number of hours in a day and then by the number of days in a month:
90 ml × 24 hours = 2,160 ml per day (or 2.16 liters per day).
2.16 liters/day × 30 days = 64.8 liters of water wasted in a month.
Step 4: Compare this with the daily water requirement of an individual.
The average daily water requirement for a person is approximately 40-50 liters.
The wasted water (64.8 liters) is enough to meet the daily water requirement of one person for about one and a half days.
This estimation shows how even small leaks can lead to significant water wastage over time, stressing the importance of fixing leaks promptly.
Something To Do
- Visit the office of your nearest ‘Jal Board’ and learn about the measures that are taken to ensure supply of clean drinking water to all the residents of the area. Prepare a project report on this.
Answer – To prepare the project report, visit your local ‘Jal Board’ office and inquire about the following:
The process of water treatment before it reaches the residents (e.g., filtration, chlorination, etc.).
The sources of water supply (e.g., lakes, rivers, reservoirs).
The maintenance and monitoring of water pipelines.
How the water quality is tested and ensured to be potable.
Steps taken to address issues like water contamination or pollution.
After gathering this information, summarize the procedures and methods used by the ‘Jal Board’ to ensure safe drinking water for the community.
- Survey your nearby locality and note down the details of the type of water purifiers, if any, used by different residents, for getting clean and safe drinking water. Present your findings on an appropriate bar chart.
Answer – For the survey, go around your neighborhood and ask the residents about the type of water purifiers they use. Common options include:
RO (Reverse Osmosis) filters
UV (Ultraviolet) filters
Activated carbon filters
Sediment filters
Once you have collected the data, present it in a bar chart. For example, the x-axis could represent the different types of purifiers (RO, UV, etc.), and the y-axis could represent the number of households using each type of purifier. This will give a visual representation of which purifier is most popular in your locality.
- Visit you local doctor, or nearby health centre, to know about the common water borne diseases in the community. Find out the details of the steps, or measures, that are being taken by the government, as well as non-government organisations, to minimise the occurrence of these diseases.
Answer – Visit your local doctor or health center to inquire about common waterborne diseases, such as:
Cholera
Typhoid
Dysentery
Hepatitis A
Ask about the symptoms, preventive measures, and treatments for these diseases.
Additionally, inquire about the steps being taken by government health authorities and non-government organizations (NGOs) to minimize the spread of waterborne diseases. These steps might include:
Awareness campaigns about the importance of clean drinking water.
Installation of water filtration systems in community areas.
Regular testing and chlorination of public water sources.
Distribution of free water purification tablets in areas with poor water quality.
Promotion of sanitation practices like handwashing and proper waste disposal.
Write a report summarizing your findings, including the preventive measures and actions taken by various organizations.
Additional Questions and Answers – 01
Fill in the blanks:
- ___________ is the method of removing suspended particles from water by adding alum.
Answer – Coagulation
- ___________ is a chemical method used to purify water and kill harmful microorganisms.
Answer – Chlorination
- Water pollution can cause a decrease in the ___________ level in water, which harms aquatic life.
Answer – dissolved oxygen
- The main source of ___________ pollution is the discharge of untreated sewage into rivers.
Answer – water
- ___________ is a water pollutant that originates from oil spills in oceans and seas.
Answer – Oil
6.___________ is a process that involves passing water through various layers of sand, gravel, and charcoal to purify it.
Answer – Filtration
- Water pollution caused by ___________ and ___________ can lead to the contamination of groundwater sources.
Answer – pesticides and fertilizers
- The release of untreated industrial ___________ into rivers leads to water pollution and harm to aquatic organisms.
Answer – effluents (or waste)
- The presence of ___________ in water can make it unsafe for drinking and can cause waterborne diseases.
Answer – pathogens (or bacteria/viruses)
- The treatment of water using ___________ helps kill harmful bacteria and make it safe for consumption.
Answer – chlorine (or chlorination)
Match the Columns:
Column A Column B
- Potable Water a) Can cause waterborne diseases
- Sewage pollution b) Water safe for drinking
- Chlorination c) Adds chlorine to water
- Industrial waste d) Main cause of water pollution
- Algal growth in water e) Depletes oxygen levels
- Waterborne diseases f) Causes harmful illness
Answer –
- Potable Water → b) Water safe for drinking
- Sewage pollution → d) Main cause of water pollution
- Chlorination → c) Adds chlorine to water
- Industrial waste → e) Depletes oxygen levels
- Algal growth in water → a) Can cause waterborne diseases
- Waterborne diseases → f) Causes harmful illness
Assertion-Reason Type Questions:
- Assertion: Chlorination is an effective method of purifying drinking water.
Reason: Chlorination kills harmful microorganisms like bacteria and viruses in the water.
- a) Both Assertion and Reason are correct.
- b) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
- c) Assertion is correct, but Reason is incorrect.
- d) Both Assertion and Reason are incorrect.
Answer – a) Both Assertion and Reason are correct. (Chlorination kills microbes, making water safe.)
- Assertion: The discharge of industrial waste directly into rivers leads to water pollution.
Reason: Industrial waste contains toxic chemicals that contaminate water and harm aquatic organisms.
- a) Both Assertion and Reason are correct.
- b) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
- c) Assertion is correct, but Reason is incorrect.
- d) Both Assertion and Reason are incorrect.
Answer – a) Both Assertion and Reason are correct. (Industrial waste contains toxins, polluting water.)
- Assertion: Water pollution caused by oil spills harms marine life.
Reason: Oil spreads on the surface of water and prevents oxygen from dissolving into the water.
- a) Both Assertion and Reason are correct.
- b) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
- c) Assertion is correct, but Reason is incorrect.
- d) Both Assertion and Reason are incorrect.
Answer – a) Both Assertion and Reason are correct. (Oil spills block oxygen, harming marine life.)
Assertion: Waterborne diseases like cholera can be prevented by using clean and safe drinking water.
Reason: Safe drinking water does not contain harmful microorganisms that cause diseases.
- a) Both Assertion and Reason are correct.
- b) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
- c) Assertion is correct, but Reason is incorrect.
- d) Both Assertion and Reason are incorrect.
Answer – a) Both Assertion and Reason are correct. (Safe water lacks disease-causing microbes.)
True/False:
- Water pollution is caused by the presence of harmful substances such as industrial waste, sewage, and agricultural chemicals. (True/False)
Answer – True (Industrial waste, sewage, and agricultural chemicals pollute water.)
- The process of filtering water through layers of sand, gravel, and charcoal removes harmful microorganisms. (True/False)
Answer – False (Filtration removes particles, but not all microorganisms; disinfection is needed.)
- Industrial waste is the only source of water pollution in rivers and lakes. (True/False)
Answer – False (Other sources include sewage, agricultural runoff, and oil spills.)
- Oil spills in the ocean do not affect marine life. (True/False)
Answer – False (Oil spills suffocate marine life and disrupt ecosystems.)
- The boiling of water is an effective method for purifying water by killing germs. (True/False)
Answer – True (Boiling kills germs, making water safer.)
- Water purification through chlorination ensures that water is free from harmful chemicals. (True/False)
Answer – False (Chlorination kills microbes but doesn’t remove all chemicals.)
- Water pollution has no impact on human health. (True/False)
Answer – False (Water pollution causes diseases like cholera and dysentery.)
- Algal growth in water bodies can deplete the dissolved oxygen levels, harming aquatic life. (True/False)
Answer – True (Algal blooms consume oxygen, killing aquatic life.)
Short Answer Questions:
- What is the process of chlorination and how does it purify water?
Answer – Chlorination is the addition of chlorine (gas or tablets) to water. It kills bacteria, viruses, and other harmful microorganisms, making water safe for drinking.
- How do oil spills affect marine ecosystems?
Answer – Oil spills form a layer on water, blocking sunlight and oxygen, leading to the death of marine organisms. They also poison fish and birds, disrupting the food chain.
- What are the main causes of water pollution?
Answer – Industrial waste discharge
Untreated sewage
Agricultural runoff (pesticides/fertilizers)
Oil spills
Plastic waste
- Define potable water. What are its main characteristics?
Answer – Potable water is safe for drinking—free from harmful chemicals, pathogens, and impurities. It should be clear, odourless, and tasteless.
- Why is sewage considered a major water pollutant?
Answer – Sewage contains disease-causing microbes, organic waste, and chemicals that deplete oxygen in water, harming aquatic life and human health.
Long Answer Questions:
- Describe the different methods of purifying water and explain how each method works. Include examples of when to use each method.
Answer – Methods of Water Purification
Filtration: Removes suspended particles using sand, gravel, and charcoal.
Boiling: Kills germs but does not remove chemicals.
Chlorination: Disinfects water using chlorine.
UV Treatment: Uses ultraviolet light to kill microbes.
Reverse Osmosis: Removes dissolved salts and chemicals.
- Discuss the harmful effects of water pollution on human health and the environment. Provide examples of diseases caused by contaminated water.
Answer – Effects of Water Pollution
Human Health: Causes cholera, dysentery, and hepatitis.
Environment: Kills aquatic life, disrupts ecosystems, and causes eutrophication.
- Explain the causes and consequences of eutrophication in water bodies. What measures can be taken to prevent it?
Answer – Eutrophication
Causes: Excess nutrients (nitrates/phosphates) from fertilizers cause algal blooms.
Effects: Algae decompose, depleting oxygen, killing fish.
Prevention: Reduce fertilizer use, treat sewage before discharge.
- How does the discharge of industrial waste into rivers affect aquatic life and the surrounding ecosystem? Suggest preventive measures.
Answer – Industrial Waste Impact & Solutions
Effects: Toxic chemicals poison aquatic life, reduce oxygen.
Solutions: Treat effluents before discharge, enforce strict regulations.
- Discuss the role of government and non-government organizations in controlling water pollution and ensuring the supply of clean water to communities.
Answer – Role of Government & NGOs
Government: Enforce pollution laws, build treatment plants.
NGOs: Raise awareness, promote clean water initiatives.
Additional Questions and Answer – 02
Fill in the Blanks:
- Water covers nearly ______ of the Earth’s surface.
Answer: three-fourth
- The presence of ______ in water can cause bad taste and offensive odour.
Answer: pollutants
- ______ is the process of adding alum to water to settle suspended impurities.
Answer: Loading
- Water fit for drinking is called ______ water.
Answer: potable
- ______ is a chemical method of purifying water by adding chlorine tablets.
Answer: Chlorination
- Oil spills in oceans harm ______ life.
Answer: marine
- The ______ of sewage involves churning and settling heavier particles.
Answer: treatment
- The principle of ______ encourages reducing, reusing, and recycling water.
Answer: 3R’s
- ______ in water bodies can deplete oxygen, harming aquatic animals.
Answer: Algae/Bacteria
- A dripping tap can waste ______ litres of water annually.
Answer: thousands
Match the Columns:
Column A (Pollution Source) Column B (Effect)
Industrial waste (a) Promotes algae growth, depletes oxygen
Domestic sewage (b) Contains harmful chemicals like heavy metals
Agricultural runoff (c) Causes oil spills, harms marine life
Oil tankers (d) Introduces pesticides/fertilizers into water
Acid rain (e) Lowers pH, harms aquatic life
Answers:
1 – (b), 2 – (a), 3 – (d), 4 – (c), 5 – (e)
Assertion-Reason Questions:
Directions: Choose the correct option:
- Both Assertion (A) and Reason (R) are true, and R explains A.
- Both A and R are true, but R does not explain A.
- A is true, but R is false.
- A is false, but R is true.
- Assertion (A): Boiling water kills germs.
Reason (R): High temperature denatures microbial proteins.
Answer: A (Both true; R explains A scientifically).
- Assertion (A): Alum is used in water purification.
Reason (R): Alum dissolves all pollutants in water.
Answer: C (A is true; R is false—alum only settles suspended particles).
- Assertion (A): Agricultural runoff pollutes groundwater.
Reason (R): Fertilizers percolate into soil and contaminate water.
Answer: A (Both true; R explains A).
- Assertion (A): Chlorination is unsafe if overused.
Reason (R): Excess chlorine forms toxic byproducts.
Answer: A (Both true; R explains A’s caution).
- Assertion (A): Water scarcity is caused only by poor rainfall.
Reason (R): Deforestation reduces groundwater recharge.
Answer: D (A is false—scarcity has multiple causes; R is true).
Short Answer Questions:
- List two visible signs of water pollution.
Answer – Bad taste/odour, unchecked weed growth, oil floating on water.
- Why is potable water essential?
Answer – Prevents water-borne diseases (e.g., jaundice, diarrhea).
- Name two methods to purify water at home.
Answer – Boiling, filtration (using sand/charcoal).
- How does sewage harm aquatic life?
Answer – Promotes algae growth, which depletes oxygen in water.
- What is “loading” in water treatment?
Answer – Adding alum to clump suspended particles for easy removal.
Long Answer Questions:
- Explain the causes and effects of water pollution.
Answer – Causes: Industrial waste, sewage, agricultural runoff, oil spills.
Effects: Harm to aquatic life, health risks, oxygen depletion.
- Describe steps to conserve water in daily life.
Answer – Use buckets instead of showers, fix leaks, reuse water for plants.
Compare filtration and chlorination as water purification methods.
Filtration: Removes physical impurities (sand/charcoal).
Chlorination: Kills microbes chemically (chlorine tablets).
MCQs
MCQs:
Which is not a water pollutant?
- a) Fertilizers
- b) Oxygen ✅
- c) Oil spills
- d) Industrial chemicals
What does alum do in water treatment?
- a) Kills bacteria
- b) Settles suspended particles ✅
- c) Adds minerals
- d) Changes water colour
True/False:
Potable water must be tasteless and odourless. (True)
Deforestation has no impact on water scarcity. (False—it reduces groundwater recharge).
Acid rain increases the pH of water bodies. (False—it lowers pH).
Activity-Based Question:
Observe water samples from different sources (tap, pond, river). Record:
Smell: Tap (odourless), Pond (musty), River (variable).
pH: Use pH paper (Tap ~7, Pond/River may be acidic/basic).
Colour: Tap (clear), Pond/River (may be turbid).