Water Treatment PDF

water treatment Short Notes on Water Treatment 1. Hard and Soft Water Hard Water: Contains dissolved salts of calcium and magnesium. Forms scales in boilers and kettles. Soft Water: Free from calcium and magnesium salts. Suitable for domestic and industrial use. 2. Disadvantages of Hard Water...

water treatment Short Notes on Water Treatment 1. Hard and Soft Water Hard Water: Contains dissolved salts of calcium and magnesium. Forms scales in boilers and kettles. Soft Water: Free from calcium and magnesium salts. Suitable for domestic and industrial use. 2. Disadvantages of Hard Water Reduces soap efficiency. Causes scaling in pipes, boilers, and utensils. Increases fuel consumption. 3. Softening of Water Ion Exchange Process: Replaces calcium and magnesium ions with sodium ions using ion- exchange resins. Hot Lime-Soda Process: Removes temporary and permanent hardness using lime (Ca(OH)₂) and soda ash (Na₂CO₃). Reverse Osmosis (RO): Water is passed through a semi-permeable membrane under pressure to remove impurities. 4. Hardness Determination EDTA Method: Ethylenediaminetetraacetic acid is used to measure total hardness. Winkler's Method: Measures dissolved oxygen (DO) in water using titration. 5. Treatment for Domestic Use Aeration: Adds oxygen to remove dissolved gases like CO₂ and H₂S. Sedimentation: Allows heavy particles to settle at the bottom. Disinfection: Uses chemicals (e.g., chlorine) or UV light to kill harmful microorganisms. Important Questions with Answers 1. Define hard and soft water. Hard Water: Contains dissolved calcium and magnesium salts. Soft Water: Free from these salts, suitable for domestic use. 2. Explain the disadvantages of hard water. Reduces soap effectiveness. Causes scale formation in boilers. Increases fuel costs due to reduced heat transfer efficiency. 3. Describe the ion-exchange process. In this process, calcium and magnesium ions are replaced by sodium ions using cation-exchange resins. Water passing through these resins becomes soft. 4. Write a note on the hot lime-soda process. Lime (Ca(OH)₂) removes temporary hardness by precipitating CaCO₃ and Mg(OH)₂. Soda ash (Na₂CO₃) removes permanent hardness by converting Ca²⁺ and Mg²⁺ into insoluble precipitates. 5. What is reverse osmosis (RO)? A process where water is forced through a semi-permeable membrane to remove dissolved impurities under high pressure. 6. Explain the EDTA method for determining hardness. A titration method where EDTA reacts with calcium and magnesium ions to form a complex. The volume of EDTA used determines hardness. 7. What is aeration in water treatment? Aeration introduces air into water to remove gases like CO₂ and H₂S and oxidize iron and manganese. 8. Describe sedimentation and its importance. Sedimentation allows heavy particles to settle at the bottom, making water clearer for further treatment. 9. How is dissolved oxygen (DO) measured using Winkler’s method? In Winkler's method, dissolved oxygen reacts with manganese sulfate and alkali-iodide azide to form a precipitate. The titration determines DO concentration. 10. What is disinfection, and why is it necessary? Disinfection kills harmful microorganisms in water using chemicals like chlorine or UV light, ensuring safe drinking water.... Explain the Ion-Exchange Process for Water Softening. Answer Outline: 1. Introduction: Definition of ion-exchange process. Importance of water softening. 2. Principle: Exchange of calcium (Ca²⁺) and magnesium (Mg²⁺) ions with sodium (Na⁺) ions using resins. 3. Types of Resins: Cation-Exchange Resin: Removes positively charged ions (e.g., Ca²⁺, Mg²⁺). Anion-Exchange Resin: Removes negatively charged ions (e.g., Cl⁻, SO₄²⁻). 4. Process Description: Hard water passes through resin beads. Na⁺ ions from the resin replace Ca²⁺ and Mg²⁺ ions. Resin regeneration using brine solution (NaCl). 5. Advantages: Highly efficient. Removes all hardness. 6. Disadvantages: High initial cost. Regular maintenance required. 2. Explain the Hot Lime-Soda Process in Detail. Answer Outline: 1. Introduction: Method to remove both temporary and permanent hardness. Suitable for industrial water treatment. 2. Chemicals Used: Lime (Ca(OH)₂): Removes temporary hardness by precipitating CaCO₃ and Mg(OH)₂. Soda Ash (Na₂CO₃): Converts permanent hardness into insoluble carbonates. 3. Reaction Mechanism: Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃ ↓ + 2H₂O Mg(HCO₃)₂ + Ca(OH)₂ → Mg(OH)₂ ↓ + CaCO₃ ↓ + 2H₂O CaCl₂ + Na₂CO₃ → CaCO₃ ↓ + 2NaCl 4. Process Steps: Mixing hard water with lime and soda. Allowing precipitates to settle. Removing softened water from the top. 5. Advantages: Reduces hardness significantly. Low cost compared to other methods. 6. Limitations: Cannot remove dissolved salts like sodium and potassium. Produces sludge, requiring disposal. 3. Describe the EDTA Method for Determination of Hardness in Water. Answer Outline: 1. Introduction: Definition of water hardness. EDTA as a complexing agent. 2. Principle: EDTA reacts with Ca²⁺ and Mg²⁺ ions to form stable complexes. The endpoint is indicated by an Eriochrome Black T indicator, which changes color. 3. Materials and Chemicals: Hard water sample. EDTA solution. Eriochrome Black T indicator. Buffer solution (to maintain pH ~10). 4. Procedure: Take a measured volume of hard water in a conical flask. Add buffer solution and indicator. Titrate with EDTA solution until color changes from wine-red to blue. 5. Calculation: Total hardness = (Volume of EDTA × Molarity of EDTA × 1000) / Volume of water sample. 6. Applications: Used in industries to test water quality. Helps in designing water treatment systems. 4. Explain the Winkler’s Method for Dissolved Oxygen (DO) Determination. Answer Outline: 1. Introduction: Importance of dissolved oxygen in water. Winkler’s method as a titration-based technique. 2. Principle: DO reacts with manganese sulfate and potassium iodide in an alkaline solution. Produces iodine equivalent to the amount of oxygen present. 3. Materials and Chemicals: Manganese sulfate, potassium iodide, and sulfuric acid. Sodium thiosulfate solution for titration. 4. Procedure: Add MnSO₄ and alkali-iodide azide to the water sample. Allow precipitate formation and add H₂SO₄ to dissolve it. Titrate with sodium thiosulfate until yellow color disappears. Add starch indicator, titrate till blue color disappears. 5. Calculation: DO in mg/L = (Volume of titrant × Normality of thiosulfate × 8) / Volume of sample. 6. Applications: Assessing water quality in rivers, lakes, and treatment plants. 5. Discuss the Domestic Water Treatment Process. Answer Outline: 1. Introduction: Importance of clean water for domestic use. Methods to remove impurities. 2. Steps in Domestic Water Treatment: Aeration: Introduces oxygen, removes dissolved gases like CO₂ and H₂S. Sedimentation: Allows heavy particles to settle. Coagulation and Flocculation: Adds chemicals like alum to clump fine particles. Filtration: Passes water through sand and gravel to remove suspended solids. Disinfection: Kills pathogens using chlorine or UV light. 3. Advanced Techniques: Reverse osmosis for better impurity removal. Activated carbon filters for odor and taste improvement. 4. Advantages: Provides safe, drinkable water. Reduces risk of waterborne diseases. 5. Challenges: Cost of advanced technologies. Regular maintenance required.