Water is our most important resource, when it is used in heating & cooling systems. There are number of problems that can arise independently the sources of supply ie. Lakes, Rivers, Well or Municipality.
It is difficult to envision the range of problems that the life sustaining substance can cause. Hardness Salts primarily calcium and magnesium carbonates have reverse solubility this means that these salts are at equilibrium at any given temperature but as water is heated, this equilibrium is upset and in order to re-establish equilibrium at the elevated temperature the amount of hardness salts that water can keep in solution must decrease. The result of all this is precipitation of the excess hardness which manifests itself as a scale deposit on heat transfer surfaces. This deposit acts as an insulator and inhibits the efficient transfer of heat. The result is fuel inefficiencies with boiler tube rupture due to overheating and increase maintains cost. Microbiological organisms can infect ion exchange resins, rendering them useless.
Treatment programs whether applied to Steam Generators, Open Recalculating Cooling Systems, Hot Water or Chilled Water Systems are designed to maximize the useful life of welted component at an acceptable cost while minimized negative environmental impact on the receiving streams. Normally treatment is through mechanical means i.e. Filtration, clarification, Ion Exchange, Degasification and Decoration. The effluent from these pre-treatment streams is then chemically treated to render benign those impurities that have escaped the pre treatment phase this is accomplished through the judicious application of chemical formulation The appropriate product in right amount at the proper feed point (optimizing chemical feed). Where replacement of existing treatment program would result in cost saving and for improved protection then such a change is proposed and the recommended program is evaluated for both performance and cost effectiveness. Our approach provides a true service program rather then a sale effort that so disguised as a service program.
It is one of our primary goals to design a water treatment program that is fully compatible with plant operations. A well designed water treatment program complements plant operations rather than call for changes in procedures to accommodate the treatment program.
No water treatment programs will live up to its potential in the absence of
proper control.
Why Should Purify Water
Water is nature's most wonderful, most abundant and most useful compound. Presence of impurities in the water, limiting its application and requires treatment before water can be used.
The substance contained in natural or raw water can be listed broadly as follows:-
1) Suspended Impurities are dispersion of solid particles that are large enough to be removed by filtration or settling. The particles which are lighter than water float on the surface.
Suspended impurities include:
(a) Clay silt --- causes turbidity
(b) Bacteria --- some cause disease.
(c) Algae, Protozoa ---- cause order, colour and turbidity.
2) Dissolved inorganic impurities. Some impurities are dissolved in water when it moves over the rocks, soil, etc., These include :
| Calcium and Magnesium
|
Bicarbonate--causes
alkalinity and hardness.
Carbonate--
---- Do -----
Sulphate--cause
hardness
Chloride
----
-------
Do
-----
|
| Sodium
|
Bicarbonate--causes
alkalinity and softening.
Carbonate--
-------
Do
-----
Fluride--cause
molted enamel of teeth
Chloride--cause
taste
|
| Metals and Oxide
|
Mangages--produces blak or brown colour
Iron Oxide--cause taste, hardness, corrosiveness and red colour.
Lead--causes arsenic poisoning
|
| Gases
|
Hydrogen
sulphide--causes foul rolten egg smell, acidity
and
corrosion of metals
|
3) Organic Impurities include :
|
Suspended
|
Vegetable---imparts
colour taste and acidity.
Animal
(dead) ---- produces harmful disease germs.
|
|
|
|
|
Dissolved
|
Vegetable
---- produces bacterias
Animal
---- causes pollution of water and produces
disease germs.
|
1) pH
2) Conductivity
3) Total Dissolved Solids
4) Alkalinity
5) Total Hardness
6) Chlorides
7) Iron
8) Silica
9) Sulphite
pH:-
pH is a measure of the concentration of hydrogen ion. It is defined as follows:
pH = -log(H+)
where (H+) is the activity of the hydrogen ion (activity in most cases is equivalent to concentration
A neutral solution is defined to have a pH of 7 and as the solution becomes more acidic (an excess of H+ ion) the pH drops below 7. As the solution becomes more basic (an excess of OH- ion) the pH increases. The pH scale varies between pH = 1 where the H+ concentration is 1 Molar (very acidic) to pH = 14 where the OH- concentration is 1 Molar (very basic).
Alkalinity:-
Alkalinity in water is due to presence of bicarbonates, carbonates and hydroxyed ions. In raw water alkalinity is mainly due to bicarbonates; however, sometime carbonates may also be present. Out of three ions only two ions can exist in any systems. That is OH, CO3, or HCO3 can either exist alone or in combination with one more ions.
P Alkalinity :-Alkalinity to phenolphthalein represents alkalinity due to OH ions plus ½ CO3 (pH 8.3)
Total Alkalinity :- Alkalinity to methyl orange represents alkalinity due to OH ion plus CO3 ion plus HCO3 ions (pH 4.3)
Relation between HO, CO3, HCO3 and total Alkalinity
|
I
/
|
Hydroxide
is
|
Carbonates
is
|
Bicarbonate
is
|
Total Alkalinity is
|
|
P = Nil
|
Nil
|
Nil
|
M
|
M
|
|
2P
< M
|
Nil
|
2P
|
M
– 2P
|
M
|
|
2P
= M
|
Nil
|
2P
|
Nil
|
M
|
|
2P
> M
|
2P
– M
|
2(M
– P)
|
Nil
|
M
|
|
P > M
|
M
|
Nil
|
Nil
|
M
|
Total Hardness
Total Hardness of water represents the sum of the concentration of all metallic cations, other than the cations of the alkali metals and is expressed as equivalent CaCO3 concentration in ppm. In most waters, nearly all hardness is due to Ca and Mg ions; but in some waters measurable concentration of Fe, Al, Mn, Zn and others may be present.
Calcium
In vast majority of raw water calcium is the main source of hardness. In boiler and cooling water systems calcium salts are the main cause of scale.
Although calcium is primarily known for its scale forming tendencies, it also acts as cathodic corrosion inhibitor. All factors being equal, water containing calcium salt will not be as corrosive as soft water.
Magnesium
Magnesium usually forms hydroxides or silicates in boiler water, which are desirable types of sludge. If boiler water alkalinity is low, undesirable magnesium phosphate often forms which
is sticky and scale forming. In cooling water system, magnesium only precipitates when pH is over 10.0.
Relation between Total Hardness( TH ) And Total Alkalinity (M)
|
If
|
Non
Alkaline Hardness is
|
Alkaline
Hardness is
|
Total
Sodium Alkalinity is
|
|
TH
> M
|
TH
- M
|
M
|
Nil
|
|
TH
= M
|
Nil
|
TH
|
Nil
|
|
TH
< M
|
Nil
|
TH
|
M
– TH
|
Chloride
All chloride salts are highly soluble in water, so scale is not a problem when chloride salts are concerned, but they are very corrosive in oxidizing environmental. Chloride is prominent in crevice corrosion and pitting all.
Sulphate
Most raw water contains sulphate. Presence of sulphate aggravates corrosion and be objectionable in concentrating water high in calcium, as in evaporative systems.
Iron
Iron is normally found in soluble ferrous Iron. On contact with air oxidizing agents, iron is converted to ferric iron and iron insoluble hydroxides or oxides. It will support to growth of iron bacteria and sulphate reducing bacteria.
Silica
Silica is present in almost all minerals and is found in fresh water. Silica is objectionable at high concentration in cooling tower makeup, because at this uncertainty about its solubility limit. It is objectionable in boiler feed water makeup is not only because it may from a scale in the boiler itself, but also because it volatility's at high temperature and pressure and redeposit on turbine blades.
Conductivities
The specific conductivity of water is a measure of its ability to conduct an electrical current. It is important as a direct measure of total amount of dissolved minerals and gases in the water.
Total Dissolved Solids (TDS)
The term total dissolved solid refers to the matter that remains as residue upon evaporation of filtered water. |
