This document discusses various topics related to water treatment and pollution. It begins by defining environmental pollution and the main types: air, water, soil, noise, radiation, and thermal pollution. It then focuses on water pollution, describing it as the introduction of contaminants into fresh or ocean waters that degrade water quality. The document outlines various water impurities like dissolved gases, salts, suspended matter, and organic matter. It also discusses parameters for assessing domestic and boiler feed water quality. Methods for hard water treatment like lime soda and ion exchange processes are explained. The document concludes with topics like desalination, sewage treatment, and the Winkler method for biochemical oxygen demand testing.

1. WATER TREATMENT
THOSHINA THOMAS
KEYI SAHIB TRAINING COLLEGE
TALIPARAMBA

2. What is meant by Environmental pollution ?
Environmental pollution is defined as the undesirable change in
physical, chemical and biological characteristics of our air, land and
water.
As a result of over-population, rapid industrializations, and other
human activities like agriculture and deforestation etc., earth became
loaded with diverse pollutants that were released as by-products.

3. Classification of Environmental Pollution
- Pollution can be broadly classified according to the components of
environment that are polluted. Major of these are:
Air pollution
Water pollution
Soil pollution
Noise pollution
RADIATION POLLUTION
THERMAL POLLUTION

4. Overview of main health effects on humans from some common types of pollution.

5. Earth- a blue planet
97% ocean
3% fresh water (2% locked in polae ice caps)

6. Sources of water:
rain water, sea water, river water, lake water, spring
water, well water etc.
Rain water is supposed to be the purest
among all and dissolves only little
amount of gases and suspended
particles from the atmosphere

7. WATERPOLLUTION
Water pollution is the introduction into fresh or ocean waters of
chemical, physical, or biological material that degrades the quality of
the water and affects the organisms living in it.
This process ranges from simple addition of dissolved or
suspended solids to discharge of the most insidious and persistent toxic
pollutants (such as pesticides, heavy metals, and nondegradable,
bioaccumulative, chemical compounds).

8. impurities present in water
Dissolved gases:
Dissolved salts:
Suspended matter: They cause turbidity of water. They
can be removed by filtration or settling.
Microscopic impurities: They may lead to water borne
diseases.
Organic matter: These may include decayed plants and
animals as impurities.

9. Parameters for checking water quality for domestic use
The parameters for checking water quality for domestic use are a follows
(i) Water should not contain hardness (not more than 300 ppm)
(ii) Turbidity should not be more than 10 ppm.
(iii) pH of domestic water should be around 7.5 — 8.0.
(iv) Coloured impurities should not be more than 20 ppm.
(v) Water should not contain dissolved solids more than 500 ppm.
(vi) Water should be free from disease producing micro organisms.
(vii) Water should be free from minerals like Pb, Arsenic, Chromium, Mn etc.
(viii) Water should be odourless and pleasant in taste.

10. The specifications of boiler feed water are as follows
(i)Water for boilers: Boiler feed water should be free from
soluble salts of Mg2+
and Ca2+
(ii) It should not contain any
organic matter.
(iii) Boiler feed water should be free from suspended
impurities.
(iv) Boiler feed water should not be acidic or alkaline.

11. Hardness of water: Hard water is one which does not produce
lather with soap solution readily, but forms a white curd.
soft water gives lather easily on shaking it with soap solution.
Alternatively hard water contains dissolved calcium and
magnesium salts; while soft water does not contain dissolved
calcium and magnesium salts in it.
CaCl2 + C17H35COONa → (C17H35COO)2Ca + 2NaCl

12. Types of hardness:
1.Temporary hardness:
2.Permanent hardness:

13. Temporary hardness:
 due to the presence of bicarbonates of calcium and
magnesium and other heavy metals and the carbonate of
iron.
 removed by heating; because on boiling the bicarbonates
of calcium and magnesium get decomposed to insoluble
carbonates which get precipitated hence can be removed.
 Therefore it is called Temporary hardness.

14. Permanent hardness:
due to the presence of chlorides and sulphates of
Calcium and magnesium iron and other heavy
metals.
It cannot be removed by heating but can be removed
by only special chemical treatments.
Total hardness: temporary + permanent hardness.

15. Disadvantages of hard water in domestic and industrial use
Hardwater, when used for bathing and washing
purposes, does not producing lather freely with soap. As
a result cleansing quality of soap is decreased and a lot
of water is wasted.
Hardwater reacts with soap it produces sticky insoluble
precipitates of calcium and magnesium soaps (scum).
For cooking the boiling point of water is increased
because of presence of salts. Hence more fuel and time
are required.
Hardwater lead to possibility of forming calciumoxalate
crystals in urinary tracks is increased.

16. In Textile Industry, Hardwater causes wastage of soap. Scums
adhere to the fabrics and cause problem.
Similarly the dissolved salts in hardwater may reacts with
costly dyes forming precipitates.
Hard water if used in sugar refining, causes difficulties in the
crystallization of sugar. (give de-liquescent sugar).
Hardwater may cause some undesirable products while
preparation of pharmaceutical products and quality of the
paper in paper industry.
Water containing chlorides and sulphates, if used for concrete
making, affects the hydration of cement and the final strength
of the hardened concrete.

17. If hardwater is fed directly to the boilers (For steam
generation), there arise many troubles such as.. Scale
and sludge formation, Hardwater may cause caustic
embrittlement which is a type of boiler corrosion.
Lime scale furring of kettles and pipes.
The fur is the insoluble carbonate formed
The deposits of lime scale can build up on the inside of
the pipe
restricting the flow of water or causing a blockage.
Lime scale deposits can be removed using a weak acid
(or water softner).

18. Permanent hardness: Unlike temporary hardness, permanent hardness is not
destroyed on boiling. It can be removed by following processes:
(i) Lime-soda process: In this method calculated quantity of chemicals are mixed with
water and these chemicals convert all the soluble hardness causing salts into insoluble
precipitates which may be removed by settling and filtration. For this purpose, Ca(OH)2
i.e.
lime, together with a calculated amount of sodium carbonate, Na2
CO3
(soda) is added in
requisite amount.
(ii) Zeolite process: Zeolites are naturally occurring hydrated sodium alumino
silicate minerals like (Na2
O. Al2
O3
. xSiO2
. yH2
O) capable of exchanging reversibly its sodium
ions for hardness producing ions in water.
(iii) Ion-exchange process: It is a process by which ions held on a porous,
essentially insoluble solids are exchanged for ions in solution that is brought in contact with it;

20. Water Softening Methods
The process of decreasing hardness of water is called
softening.
Temporary hardness can be removed by boiling or by
adding calculated amount of lime (calcium hydroxide) to the
hard water (Clark’s method).
Similarly removal of permanent hardness can be achieved
by the addition of washing soda (Na2CO3.10H2O).
Removal of both temporary and permanent hardness can
be done by lime soda process and ion exchange process
such as inorganic cation exchangers (Zeolites) or organic
ion exchangers.

21. 1. Lime-soda process
addition of calculated amounts of both lime [Ca(OH)2]
and soda [Na2CO3] in to hard water followed by
removal of the precipitates.
Lime soda process can be done in two different ways
such as cold lime soda process (at room temperature)
and hot lime soda process (at temperature 80-1500C).

22. 2. Ion exchange method
Ion exchange devices reduce the hardness by
replacing hardness ions (mainly Mg2+ and Ca2+) with
Na+ and K+ ions in a crystal lattice or gel.
If the exchanged ions have +ve charge, the ion
exchanger is called cationic and if they have –ve
charge, it is called as anionic.
The ion exchanger may be natural or synthetic one.

23. a) Inorganic cation exchangers
Eg. Zeolite or permutits
Zeolites are hydrated sodium alumino silicates
(Na2O.Al2O3.xSiO2.yH2O, where x = 2-10 and y =
2-6).
For convenience it is represented as Na2Z.
Zeolites have empty channels with free holes thus are
capable of exchanging their Na+ ions for Ca2+ and
Mg2+ ions of hard water.

24. The reaction can be represented as,
Ca(HCO3)2 + Na2Z → CaZ + 2NaHCO3
CaCl2 + Na2Z → CaZ + 2NaCl.

25. BOD (Biological Oxygen Demand):
It indicates the amount organic impurities present in
water, which can be oxidized by micro-organisms.
It is defined as the amount of oxygen required by the
micro-organisms, in presence of oxygen for the
biological oxidation of organic matter in a sample water,
when incubated for 5 days.
When more pollutants present more will be the, consumption of oxygen by the
microbes. Hence the amount of dissolved oxygen present decreases.
BOD can be determined by Winklers method.

26. COD (Chemical Oxygen Demand):
It accounts for the organic matter that is not oxidized
by microbes.
It is defined as the amount of oxygen required
organic matter in a sample water for it’s oxidation by
strong chemical oxidizing agents like potassium
dichromate.

27. Different Kinds of Water
Fresh Water : Only 2.75 percent of the water on Earth is fresh water, about
two-thirds of it is frozen in glaciers, a quarter is groundwater and only 0.005
percent of it is surface water. Fresh water may be either ‘hard’ or ‘soft’.
Brackish Water: Brackish water is the type of water that has salinity
between that of fresh water and seawater.
Seawater: Seawater typically contains about 3.5% sodium chloride.
Distilled/ Demineralized Water: water that is ripped of its impurities through
the process of distillation.
Potable Water: Potable water is fresh water that is sanitized with oxidizing
biocides such as chlorine or ozone to kill bacteria and make it safe for
drinking purposes.

28. Potable water
The water used for drinking purpose is called potable water. The water
should be free from organic matter, suspended impurities, and
pathogenic bacteria. The water should be safe and pleasant. The
potable Water should be
clear, colourless, odourless
Should have good taste
Should be free from pathogenic microbes
Should be free from minerals like lead, arsenic, chromium etc.
pH should be between 6.5-8.5.

29. DESALINATION
It is method to remove dissolved salt from saline water to get pure water. By
1. Electrodialysis:
2. Reverse osmosis:

30. Electrodialysis:
Principle: charged ions move towards oppositely charged electrodes
through ion selective membrane, in the presence of electric field.

31. Reverse osmosis:
When a semi-permeable membrane is placed between
brackish water (brine) and pure water, solvent (pure
water) has a natural tendency to flow into brine which is
called osmosis. But when pressure is applied to brine,
the water from brine will flow into water, which is called
reverse osmosis.
cellulose
acetate

32. Too high pressure cannot be applied, which would result in the rupture of the
membrane

33. Sewage treatment
The sewage water contains various minerals, organic
matters, suspended impurities, pathogenic bacteria etc.
Therefore water has to be treated before letting into sea.
The principal objectives in Municipal water treatment are
removal of suspended paticles,
removal of colour and
removal of disease causing bacteria.

34. Generally it consists of following methods.
1. Primary treatment (physical and chemical treatment): It
removes all the settled impurities.
Screening; The sewage water is passed through
metallic screens or bar screens.
Slit or grit removal: remove sand and broken
pieces of glass.
Oil and gas removal
Sedimentation: coagulating agent like alum is
added, to remove suspended particles

35. 2. Secondary treaetment of sewage (Biological
treatment):
This involves the removal of organic matter present in
the water.
1). Trickling filtration: Water is passed through trickling
filters during which some of the organic maters are
oxidized by the micro-organisms.
2). Activated sludge process:
The organic impurities get oxidized to carbon dioxide,
nitrogen is converted to ammonium and then to nitrites
and nitrates.

36. Tertiary treatment:
Sedimentation: Sewage water is taken in sedimentation
tank and treated with coagulant like alum to remove
suspended impurities in the form of precipitates.
Filtration: The traces of suspended impurities are are
removed by filtering through sand filters.
Degasification: removes gases like hydrogen sulphide ,
ammonia etc.
Disinfection: It is treated with chlorine in acid medium to
remove pathogenic bacteria by forming hypochlorous
acid.

37. The Winkler Fixing
Mn2+
+ 2 OH-
+ ½ O2 → MnO2 (s) + H2O
MnO2 (s) + 2 I-
+ 4 H+
→ Mn2+
+ I2 + 2 H2O
Do you see the brilliance of this two-step sequence?
The first step converts O2 to MnO2 under basic conditions.
The second step converts MnO2 to I2 under acidic
conditions. When you acidify the solution – you prevent
the first reaction!!! Any oxygen that dissolves later can’t
react!

38. We’ve seen it before:
The Residual chlorine determination
converted Cl2 to I2, then analyzed the I2 by
titration with sodium thosulfate!
I2 + 2 S2O3
2- →
S4O6
2-
+ 2 I-

39. THANK
YOU……………………