This document summarizes different advanced water treatment methods including water softening, desalination, and membrane systems. It discusses the processes of temporary and permanent water softening including boiling, lime addition, and lime-soda processes. Methods of desalination are also summarized, including distillation, electrodialysis, reverse osmosis, solar distillation, and freezing. Advantages and disadvantages are provided for various water treatment methods such as lime-soda process, zeolite exchange process, demineralization, and distillation.

1. ENVIRONMENTAL ENGINEERING-I
UNIT-IV
ADVANCED WATER TREATMENT PART-II
Sathyan S
Department of Civil
Engineering.

2. • water softening
• desalination
• membrane systems
• recent advances

3. SOFT WATER: Water, which produces lather readily with
soap solution is called soft water. Due to absence of Ca
and Mg salts.
HARD WATER: Water, which does not produce lather with
soap solution , but produces white precipitate (scum) is
called hard water.
WATER SOFTENING: The removal of hardness producing
WATER SOFTENING

4. • More quantity of soap is
consumed during laundries .
This is due to the fact that
25ppm additional soap is
required for every 1.0ppm of
hardness in water.
• The fabric of clothes get
spoiled .
• Hard water creates choke and
clog plumbing.
• It affects the manufacturing
process of textile, ice making

5. Temporary hardness:
• It is caused by carbonates and bicarbonates of Ca and Mg.it is
also called carbonate hardness.
Methods of removing temporary hardness:
1.By boiling 2.By addition of lime.
Permanent hardness:
• It is caused by sulphates, chlorides and nitrates of Ca and Mg.
Methods of removing permanent hardness:
1. Lime-Soda process . 2.Base exchange/Zeolite process .
3.Demineralisation process.

6. BY BOILING
• Ca(HCO3)2 + Heat CaCO3 + CO2 +H2O
Calcium bicarbonate Calcium carbonate(insoluble).
only for small scale purposes .

7. BY ADDITION OF LIME
• Mg(HCO3)2 + Ca(OH)2 Ca(HCO3)2 + Mg(OH)2
• Ca(HCO3)2 + Ca(OH)2 2CaCO3 + 2H2O
• Removed by sedimentation tank.

8. LIME SODA PROCESS
• Lime = bicarbonate .
• Lime & soda ash = both temporary and permanent hardness.
Method :- 1.sedimentation 2.filtration 3. both.
• Process may be operated continuously or intermittently.
• Temperature – (10-20 C) OR 100 C.

11. ADVANTAGES
• Suitable for turbid , chalybeate
• Has bacterial effect.
• Removes iron & manganese to some
amount
• Reduction in total mineral content of
water.
• More economical
• Increase pH value & decrease in corrosion
of the distribution system.
• Free from patent complications.
DISADVANTAGES
• Require skilled supervision .
• Large quantity of sludge is formed .
• Not possible to produce 0 hardness.
• Water contain insoluble salt like sodium
sulphate and cannot be used in high
pressure boilers.

12. BASE EXCHANGE OR ZEOLITE PROCESS
• Also known as cation exchange process.
Zeolite= Complex silicates of aluminium and
sodium.
Charging of zeolite:-
Softening of water:

13. ADVANTAGES
• No sludge
• Compact and small space is required.
• Process is almost automatic.
• Chemical are cheap and easy to handle.
• If pressure softener is used , repumping is
not necessary.
• Initial and operating cost are low.
DISADVANTAGES
• Unsuitable for turbid water.
• Unsuitable for water containing iron and
manganese.
• Zeolite softeners are to be handle with
care.
• Chances of bacterial growth on the bed
of zeolite .
• The by product sodium bicarbonate
cause priming and foaming in boiler
feed water .

14. DEMINERALISATION OR IRON EXCHANGE PROCESS

15. ADVANTAGES
• High acidic or alkaline water can be
treated.
• Water from this process have very
low hardness.
DISADVANTAGES
• Water containing turbidity , Fe and
Mn cannot be treated.
• The equipment and chemicals are
highly expensive costly.

16. DESALINATION
• Process of removing extra common salt or NaCl.
• These impurities will have peculiar brackish taste or salty taste .
• Seawater contains 3.5-4% of salt
• Great salt lake in Utah contains 23% of salt.
• In Gulf countries there is no alternative except to treat seawater.
METHODS:-
1.Distillation 2.Electro dialysis 3.Reverse osmosis 4.Solar distillation
5. Freezing

17. DISTILLATION
• Its is the oldest and most productive way .
• It works based on heat transfer by the source of heat energy under vacuum
pressure.
• Performance of an evaporator plant is mesure by the specific heat consumption
No. Of kilocalories required to to produced one kilogram of distilate .