hardest water

1. Lecture 9
 Water-sources-Impurities
 Hardness of water
 Types of hardness
 Degree of hardness
 Units of hardness
 Disadvantages of Hard water for Industrial and
Agricultural use

2. WATER SOURCES AND IMPURITIES
Water is nature’s most wonderful, abundant and
useful compound.
 It is not only essential for the lives of animals and
plants but also used as an engineering material in
the steam generation in industries.
 Water is also used as a coolant inpower and
chemical plants.
 In addition to it, water is widely used in other
fields such as production of steel, rayon, paper,
atomic energy, textiles, chemicals, ice, and for air-
conditioning, drinking, bathing, sanitary, washing,
irrigation, fire-fighting, etc.

3. SOURCES OF WATER
SURFACE WATERS:
1. Rain water:
 It is probably the purest form of nature water, since it is obtained
as a result of evaporation from the surface water.
 However, during the journey downwards through the
atmosphere, it dissolves a considerable amount of industrial gases
(like CO2, SO2, NO2 etc. ) and suspended particles both are of
organic and inorganic origin.

4. RAIN WATER

5. 2.River water
• Rivers are fed by rain and spring waters.
• Water from these sources flow over the
surface of land, dissolves the soluble minerals
of the soil and finally falls in rivers.
• In general, the greater the contact that water
has with the soil, or the more the soluble the
minerals of the soils with which it has come in
contact, the greater is the amount of dissolved
impurities in river water.

6. RIVER WATER

7. 3. Lake water:
• It has a more constant chemical composition.
• It, usually, contains much lesser amounts of
dissolved than even well water, but quantity
of organic matter present in it is quite high.

9. 4. Sea water:
• It is the most impure form of natural matter;
river joins Sea and throws in the impurities
carried by them.
• Moreover, continuous evaporation of water
from the surface of sea makes sea water
continuously richer in dissolved impurities.

11. • Surface water, generally, contains suspended
matter, which often contains the disease –
producing (or pathogenic) bacteria.
• Hence, such waters as such are not
considered to be safe for human
consumption.

12. Underground waters:
• A part of the rain water, which reaches the
surface of the earth, percolates into the earth.
• As this water journeys downwards, it comes in
contact with a number of mineral salts present
in the soil and dissolves some of them.
• Water continues its downwards journey, till it
meet a hard rock, when it retards upwards and
it may even come out in the form of spring.

14. • Spring and well water (or underground water), in
general, is clearer in appearance due to the
filtering action of the soil, but contains more
dissolved salts.
• Thus, water from these sources contains more
hardness.
• Usually, underground water is of high organic
purity.

15. CHARACTERISTICS IMPARTED BY IMPURITIES IN WATER
• The natural water is usually, contaminated by
different types of impurities.
• 1. Physical impurities
• (a) Colour
• (b) Turbidity
• (c)Taste
• (d) Odour

16. (a) Colour
• (a) Colour in water is caused by metallic
substances like salts of iron, manganese,
humus material, tannins, peats, algae, weeds,
protozoa, industrial effluents (from paper and
pulp, textile, tanneries etc.).
• Actually colour in water is due to dissolved
substances and substances present as fine
colloids.

17. (b) Turbidity
• It is due to the colloidal,
extremely fine suspension such
as clay, slit, finely divided matters
(organic and inorganic) micro-
organisms like plankton, etc.

18. (c)Taste
• It is, usually, interlinked directly with
odour. However, in some waste water,
taste is not accompanied by odour
• Thus, presence of dissolved mineral in
water produces taste, but not odour.

19. Example
(i) Bitter taste can be due to the presence of iron,
aluminium, manganese, sulphate or excess of
lime.
(ii) Soapy taste can be due to the presence of large
amount sodium bicarbonate.
(iii) Brackish taste is due to the presence of unusual
amount of salts.
(iv) Palatable taste is due to the presence of dissolved
gases (Co2) and minerals (like nitrates) in water.

20. (d) Odour
• Odour in water is undesirable for domestic as
well as industrial purposes.
• Disagreeable odour is water may be caused by
the presence of living organisms decaying
vegetation including algae, bacteria, fungi and
weeds.

21. (2) Chemical impurities in water includes:
• (i) inorganic and organic chemicals(some which are
toxic immature) released from dyes, paints and
vanishes, drugs,insecticides, pesticides, détergent,
pulpe and textiles, industries, tanneries, etc.
• Allthese pollute water bodies (ii) acids discharged in
water by DDT, high explosives, battery, industries,
etc.
• The use of this type of contaminated water causes
harmful effects on health of human –beings.

22. (a) Gases:
(i) All natural waters contain dissolved atmosphere CO2.
• Also polluted waters acquire CO2 from the biological
oxidation of organic matter.
• Its presence in water is no significance.
(ii) Concentration of dissolved atmospheric O2 in water
depends on temperature, pressure and salt content
in water.
• Dissolved O2 in industrial water is nuisance, since it
induces corrosion reactions.
• On the other hand, dissolved O2 in water is essential
to the life of aquatic organisms such asfishes.
• (iii) Dissolved NH3 is water arises from the
decomposition (aerobic or anaerobic)of nitrogenous
organic matter .

23. (b) Mineral matters
•Mineral matters have origin
from rocks and industrial
effluents.

24. (3) Biological impurities
• Biological impurities are algae, pathogenic
bacteria, fungi, viruses, pathogens, parasites
worms, etc.
• The sources of these contamination is discharge
of domestic and sewage wastes, excreta (from
man, animals and birds) etc.
• Microorganisms are usually; abundant in surface
waters, but their count is often quite low or even
nil in deep-well waters.

25. Hardness of water
• Hardness of water is that characteristic which
“prevents the LATHERING of soap”.
• Water which doesn't produce lather with soap
solution readily but forms a white curdy
precipitate is called hard water.
• On the other hand, water which forms lather
easily on shaking with soap solution is called
soft water.

26. Hardness of water
• Hardness of water is due to the presence of
certain salts of calcium, magnesium and other
metals dissolved in it.
• Soft water does not contain dissolved salts of
Ca, Mg in it.
• When it is treated with soap it produces lather
readily

27. Hardness of water

28. Hardness of water

29. Hardness of water
• When water flows over the land surface or
percolates through soil in gets
contaminated because he dissolved many
salts from rock and minerals and also fine
clay and silica particles get suspend in
water.
• The nature of the salts dissolved in its
make it hard or soft water.

30. Types of hardness
Two types of hardness
–Temporary or Carbonate hardness
–Permanent or non-Carbonate
hardness

31. Temporary or Carbonate hardness
• This is caused by the presence of dissolved by bicarbonates of
calcium, magnesium and the carbonates of heavy metals like
iron.
• Temporary hardness is mostly destroyed by mere boiling of
water.
• When bicarbonates are decomposed, yielding in soluble
carbonate or hydroxides which are deposited as a crust at the
bottom of the vessel. Thus

32. Permanent or non-Carbonate hardness
• This is due to the presence of chlorides and
sulphates of calcium, magnesium heavy metals
like iron and other heavy metals unlike
temporary hardness and permanent hardness is
not destroyed by boiling. It requires more
treatment.

33. Equivalent of calcium carbonate
• The concentration of hardness and non-hardness
constituting ions are usually expressed in terms
of equality amounts of CaCO3 since this more
permits the addition and subtraction of
concentration when required.
• The choice of CaCO3in particular is due to its
molecular weight (100)&equivalent weight(50).
• Further, it is the most insoluble salts that can be
precipitated in water treatment.

34. The equivalent of CaCO3 is calculated as:

35. Calculation of equivalent CaCO3

36. Units of hardness

37. Units of hardness

38. Relationship between various units of hardness

39. Disadvantages of hard water
• A. In domestic use:
–Washing
–Bathing
–Cooking
–Drinking

40. Washing
• Hard water, when used for washing purposes, does
not lather freely with soap.
• it produces sticky precipitates of calcium and
magnesium soaps.
• The formation of these insoluble sticky precipitates
continues till all calcium and magnesium salts
present in water are precipitated.
• Only after that, the show gives lather with water.
• Due to this there is wastage of lot of soap.
• Also, the sticky precipitates adhere to the fabric
giving spots and streaks.
• In addition, presence of iron salts may cause
staining of cloth.

41. Bathing
• Cleansing quality of soap is depressed
and a lot of it is wasted because hard
water instead of forming lather produces
sticky scum which gets deposited on the
body and bath-tub.

42. Cooking
• The boiling point of water is elevated due to the
presence of dissolved hardness producing salts.
• Consequently, more fuel and time are required
for cooking.
• Certain foods like pulses, beans and peas do not
cook soft in hard water.
• Tea or coffee prepared in hard water has an
unpleasant taste.
• Dissolved salts are deposited as carbonates on
the inner walls of the water heating utensils.

43. Drinking
• Hard water is poor in taste and causes bad
effect in our digestive system.
• Moreover, the possibility of forming calcium
oxalate crystals in urinary tracts is increased.