📖 Lesson 3: Water Treatment Methods

👩🏽‍🏫 Introduction

Hello again, water expert! 👋🏽

Imagine drinking water straight from a river. 😬 Even if it looks clean, it might be full of invisible germs, harmful chemicals, and dirt. That’s why water treatment is so important. Whether for a big city or your village well, treating water makes it safe and healthy.

In this lesson, you’ll learn how water is cleaned, step by step, and why each stage is essential. Let’s explore how raw water becomes the safe, clear liquid that flows from your tap.

📘 Core Concepts

🔹 What is Water Treatment?

Water treatment is the process of removing contaminants and making water safe for use—especially for drinking, cooking, and bathing.

Treated water must be:

• Colourless

• Odourless

• Tasteless

• Free of harmful microorganisms and chemicals

🔹 Sources of Water

🔹 Stages of Water Treatment (Public Supply System)

💧 1. Screening

• Removes large objects like leaves, sticks, plastics.

💧 2. Sedimentation (Settling)

• Heavy particles sink to the bottom in large tanks.

💧 3. Coagulation and Flocculation

• Chemicals like alum (aluminium sulfate) are added to clump dirt particles together.

💧 4. Filtration

• Water passes through layers of sand and gravel to remove smaller particles.

💧 5. Disinfection

• Chlorine or ozone is added to kill germs like bacteria and viruses.

💧 6. pH Adjustment

• Lime or other chemicals are used to neutralize acidic water.

💧 7. Storage and Distribution

• Clean water is stored in tanks and pumped to homes and buildings.

📊 Summary Diagram of Water Treatment

🔹 Common Water Treatment Chemicals

👨🏽‍🔬 Simple Household Water Treatment Methods

Even without a big water plant, you can treat water at home:

📐 Sample Problem Walkthrough

🧠 Problem: You are asked to design a simple water treatment system for your school using buckets and basic materials. What steps will you include?

✅ Step-by-Step Solution:

1. Pre-filtration: Use a cloth to remove large particles.

2. Sedimentation: Let water sit in a bucket for a few hours so particles settle.

3. Filtration: Pour through sand and gravel layers.

4. Disinfection: Boil the water or add a chlorine tablet.

5. Storage: Keep clean water in a covered, clean container.

✔️ Answer: Your system would include pre-filtration, sedimentation, filtration, disinfection, and safe storage.

✍🏽 Practice Exercises

1. Fill in the blanks
(a) The stage where chemicals like alum are added is called ________.
(b) ________ is commonly used to kill bacteria and viruses in water.

✅ Answers:
(a) Coagulation
(b) Chlorine

2. Match the Method to Its Function

✅ Answers:
(i) → C
(ii) → B
(iii) → A

3. Short Answer

Why is it important to adjust the pH of treated water?

✅ Sample Answer:
Adjusting pH prevents the water from being too acidic or basic, which could damage pipes and harm health. A neutral pH ensures safety and comfort for consumers.

🌀 Recap

Today, you learned that:

• Water treatment is the process of cleaning water for safe use.

• It involves steps like screening, sedimentation, coagulation, filtration, and disinfection.

• Both public and home systems use similar ideas.

• Treated water must be colourless, odourless, tasteless, and germ-free.

💭 Reflection Prompt

Look at the water you drink at home or school. Can you guess where it came from and what treatment it may have gone through? Write down the steps you think it passed through before it reached you.