Concept of Hardness of water. Types of Hardness, Temporary hardness and Permanent hardness. Calculation of Hardness

1. Mahavir Education Trust's
SHAH & ANCHOR KUTCHHI ENGINEERING COLLEGE
Chembur, Mumbai - 400 088
WATER
Dr. Archana Nath

2. Mahavir Education Trust's
SHAH & ANCHOR KUTCHHI ENGINEERING COLLEGE
Chembur, Mumbai - 400 088
•Impurities in water
•Hardness of water (Water 1)
Hardness calculation
•Hardness determination
EDTA method
•Softening of water (Water 3)
•BOD & COD (Water 4)
•Water purification (Water 5)
(Water 2)

3. Learning Objectives
You will be able to
Explain Hardness of water
Differentiate two types of hardness
Calculate Hardness of water by knowing the amount
of impurities present
Judge the required quality of water for different
industry
Mahavir Education Trust's
SHAH & ANCHOR KUTCHHI ENGINEERING COLLEGE
Chembur, Mumbai - 400 088

4. • Weight loss
• Digestion
• Brain
• Skin
• Headache Cure
• Energy
• Better exercise
🤔
Less Than 3% of the Water covering the
earth is freshwater
1 of 4 deaths of children under the age of
five are the result of water-related illness
80% of the illnesses in developing
countries result from unhealthy water
and/or sanitation system.
https://www.nrdc.org/stories/water-
pollution-everything-you-need-
know#causes
https://publicintegrity.org/environment/indu
strial-waste-pollutes-americas-drinking-
water/

5. Very Hard
Hard
Moderately hard
Soft
More than 180
120-180
60-120
0-60
Hardness (ppm)
in terms of CaCO3
Hardness- Soap consumption
Hard Water – More soap to give lather
Soft water- Less soap to give lather
2C17H35COONa + CaCl2 (C17H35COO)2Ca↓+ 2NaCl
Ca+2
Mg+2
Fe+2
Cause of Hardness
Ca+2 Mg+2 Fe+2
Al+3 other heavy
metals

6. Disadvantage of Hard water
Wastage of soap
Wastage of Fuel
Formation of scales on metallic Boilers
Problem with strength of concrete
Most affected Industries –Textile, Sugar, Paper, Pharmaceutical,
How much Hard ?
All Hardness producing salts ---Equivalent amount CaCO3
Molecular Weight of CaCO3 = 100 so Equivalent weight of
CaCO3 = 50
Equivalent weight /Gram equivalent = the mass of a given substance
combine with or displace a fixed quantity of another substance

7. Temporary hardness – Carbonate and Bicarbonate of Ca, Mg,
Fe, Al, heavy metals
Permanent Hardness – Sulphate, Chloride, Nitrate…of Ca, Mg,
Fe, Al, heavy metals
Removed on boiling
Ca (HCO3)2
by heating
CaCO3↓ + H2O + CO2
Calcium bicarbonate
Mg (HCO3)2
by heating
Mg (OH)2↓ + 2CO2
Magnesium bicarbonate

8. A sample of water is found to contains following dissolving salts in milligrams per
litre Mg (HCO3)2 = 73, CaCl2 = 111, Ca (HCO3)2 = 81, MgSO4 = 40 and MgCl2 =
95. Calculate temporary and permanent hardness and total hardness
Name of
the
hardness
causing
salts
Amount of
the
hardness
causing
salts(mg/Li
t)
Equivalent
weight of
hardness
causing
salts
Amounts equivalent to
CaCO3 (mg/Lit)
Type of
Hardness
Mg (HCO3)2 73 146/2=73 73×50/73 = 50 T
CaCl2 111 111/2=55.5 111×50/55.5 = 100 P
Ca (HCO3)2 81 162/2=81 81×50/81 = 50 T
MgSO4 40 120/2=60 40×50/60 = 33.3 P
MgCl2 95 95/2=47.5 95×50/47.5 = 100 P
Temporary hardness = Mg (HCO3)2 + Ca (HCO3)2 = 50 + 50 = 100mgs/Lit.
Permanent hardness = CaCl2 + MgSO4 + MgCl2 = 100 + 33.3 + 100 =
233.3mgs/Lit.
Total hardness =Temporary hardness +Permanent hardness = 333.3mgs/Lit

9. Leasson outcome
•Concept of Hardness of water
•Concept of Temporary and permanent Hard water
•Calculation of Hardness of water by knowing
the amount of impurities present

10. Assignment
Q.
No
Question
Marks
1 Distinguish between temporary and permanent hardness. 3
2 Calculate different type of hardness present in water containing
following salts. Ca(HCO3)2=64.8 ppm, MgCl2=9.5 ppm, NaCl =15
ppm, MgSO4=24 ppm CaSO4= 35 ppm mg/l and SiO2= 25 ppm.
4
3 Calculate Temporary permanent and total hardness of water
sample which has following impurities in mg/l. Ca(HCO3)2=162
mg/l, CaCl2=22.2mg/l, MgCl2=95, Mg(HCO3)2=7.3mg/l
CaSO4=13.6 mg/l and Na2SO4=20mg/l.
4