Water Purification Methods

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Questions and Answers

What is the primary purpose of screening in water purification?

To remove suspended particles

To remove floating matter (correct)

To remove colloidal matter

To remove bacteria and microorganisms

What is the normality of SHW in terms of CaCO3?

10mg CaCO3

15mg CaCO3 (correct)

20mg CaCO3

30mg CaCO3

What is the purpose of sedimentation tanks in water purification?

To remove bacteria and microorganisms

To add coagulants to water

To allow suspended particles to settle down (correct)

To filter out colloidal matter

What is the volume of EDTA required to titrate 20 ml of SHW?

25 ml EDTA Signup and view all the answers

What is the total hardness of the test hard water in ppm?

2160 ppm Signup and view all the answers

What is the reason for adding coagulants in sedimentation?

To produce insoluble, gelatinous, floculant precipitates Signup and view all the answers

What is the permanent hardness of the test hard water in ppm?

1440 ppm Signup and view all the answers

What is the purpose of the middle layer in a sand filter?

To retain coarse particles Signup and view all the answers

What is the temporary hardness of the test hard water in ppm?

720 ppm Signup and view all the answers

What happens to the filter bed over time in filtration?

It becomes less efficient Signup and view all the answers

How is the standard hard water prepared?

By dissolving 1g CaCO3 in dil. HCl and then making up to 1 litre with distilled water Signup and view all the answers

What is the purpose of scraping off the top sand layer in filtration?

To replace it with clean sand Signup and view all the answers

What is the volume of EDTA solution required to titrate 50 ml of the standard hard water?

48 ml EDTA Signup and view all the answers

What is the term used to describe the removal of microorganisms from water?

Disinfection Signup and view all the answers

What are the chemicals used to remove microorganisms from water called?

Disinfectants Signup and view all the answers

What is the purpose of boiling and filtering the test hard water?

To remove temporary hardness Signup and view all the answers

What is the purpose of adding EBT indicator to the Boiled Hard Water (BHW) sample?

To indicate the endpoint of the EDTA titration Signup and view all the answers

What is the normality of the Boiled Hard Water (BHW) sample if 50 ml of BHW requires 20 ml of EDTA solution?

0.2 N Signup and view all the answers

What is the classification of water hardness that is caused by the presence of calcium and magnesium ions?

Permanent hardness Signup and view all the answers

What is the calculation to determine the temporary hardness of a water sample?

Total hardness - Permanent hardness Signup and view all the answers

What is the advantage of using the EDTA titration method for determining water hardness?

It is more accurate and convenient Signup and view all the answers

What is the unit of measurement for water hardness?

ppm Signup and view all the answers

How is the Boiled Hard Water (BHW) sample prepared for EDTA titration?

By adding 10 ml of buffer solution and 3-4 drops of EBT indicator Signup and view all the answers

What is the calculation to determine the hardness of a 0.1M CaCl2 solution?

Molarity x 2 x Eqnt.Wt.CaCO3 x 1000 Signup and view all the answers

Study Notes

Methods of Water Purification

Removal of suspended impurities:
- Screening: water is passed through bar screens with many holes to remove floating matter
- Sedimentation: water is taken to big tanks for 2-6 hours, allowing suspended particles to settle down by gravity
- Sedimentation with coagulation: adds coagulants like alums, FeSO4, NaAlO2 to remove fine clay particles and colloidal matter
- Filtration: water is passed through a bed of fine sand and granular materials to remove colloidal matter, bacteria, and microorganisms

Removal of Microorganisms (Disinfection Methods)

Disinfection: removing bacteria and microorganisms from water using disinfectants
Chemicals used: precipitates are filtered off, and the filtrate is collected

EDTA Process

Used to determine water hardness
Advantages: more accurate, convenient, and rapid procedure
EDTA process involves titrating boiled hard water with standardized EDTA till the wine red color changes to blue

Calculating Hardness

Hardness = Normality x Equivalent Weight of CaCO3 x 1000
Examples: calculating hardness of 0.1M CaCl2 solution and 0.4 N Ca2+ solution

Determining Hardness of Water

Steps: preparation of standard hard water, standardization of EDTA, estimation of total hardness, determination of permanent hardness, and determination of temporary hardness
Examples: calculating total, permanent, and temporary hardness of water samples