A Comprehensive Guide about the Impact of Water,Source of it and hardness of water in Industrial Processes

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Introduction

Water is essential for life and is also crucial in a range of industrial activities. Its quality and properties are key factors in determining efficiency and environmental consequences in processes such as manufacturing and energy production. This blog will explore the influence of water, its origins, and the significance of water hardness in industrial environments.

Water is the basic necessitiy of life. It is necessary for the survival of all livings. Approximately 80% of the earth surface is covered by water, but only 1% water is available for the uses of different purposes such as domestic,agaricultural, municipal and industrial work.

Source of water

The various sources of water are:
(i) Surface waters :
     (a) Flowing water
      e.g. streams and rivers etc.
     (b) Still water
      e.g. ponds, lakes and reservoirs etc.
(ii) Underground water
     (a) Water from shallow and deep springs and wells
     (b) Water from lower measures of coal mines
(iii) Rain water
(iv) Esutarine and sea water

Types of impurities found in water

The impurities present in natural waters may be broadly classified as follows

(1) Dissolved impurities

      (a) Inorganic salts e.g.,
                    (i)Cations:
`left(Caright)^{2+}`,`left(Mgright)^{2+}`,`left(Naright)^{+}`,`left(Kright)^{+}`,`left(Feright)^{2+}` `left(AIright)^{3+}`
and sometimes traces of
`left(Znright)^{2+}`,`left(Curight)^{2+}`
                    (ii) Anions:
`left(Clright)^-`,`left(So_4right)^{-2}`,`left(No_3right)^-`,`left(HCo_3right)^-`
and sometimes
`left(No_3right)^-`,`left(Fright)^-`
    (b) Gases e.g.,`Co_2`,`O_2`,`N_2` oxides of `N_2` and sometimes `NH_3`,`H_2S`
    (c) Organic salts

(2) Suspended impurities

      (a) Inorganic e.g., clay and sand
      (b) Organic e.g., oil globules, vegetable and animal matter.

(3) Dissolved impurities

Finely divided clay and silica, aluminium hydroxide, ferric hydroxide, organic waste products, humic acids, colouring matter, complex protein, aminoacids,(which are generally classified as albunoid ammonia).

(4) Bacterial impurities

Bacteria, other micro-organisms and other forms of animal and vegetable life.
Purpose Specifications and Remark
Paper Industry (a) Free from alkalinity (alkaline water consumes more alum, thereby
increasing the cost of production).
(b) Free from hardness: (Calcium and magnesium salts increase the ash
content of the paper produced).
(c) Free from colour, turbidity and salts of Fe and Mn : (colour and
brightness of the paper are affected by the above impurities).
(d) Free from Silica : (Silica causes cracks in the paper).
Textile industry (a) Free from turbidity : (turbidity causes uneven dyeing).
(b) Free from colour, and salts of Fe and Mn : (these impurities cause
stains on the fabric).
(c) Free from hardness and organic matter : (Hard water reduces the
solubility of acidic dyes and causes precipitation of basic dyes. They
also render the dyeing non-uniform. Organic matter may cause foul smell
of the product).
Thermal Power Generation industry (a) Boiler feed Water : Free from hardness : (hard water causes
scaleformation on boiler metal surface, thereby reducing heat transfer
efficiency and causing shut-down or even accidents).
(b) Cooling water : The water should be non-scale forming,
non-corrosive, and should not permit the growth of algae. Scale and
algae reduce the heat transfer efficiency and interfere with free flow
of water.
Dairy industry The water should be colourless, odourless, and tasteless. It should be
free from pathogenic organisms.
Beverage industry The water should be pure. It should not be alkaline, because alkalinity
in water tends to neutralise the fruit acids and distorts the taste.
Laundry The water should be free from colour, hardness and salts of Fe and Mn :
(Hardness of water increases the consumption of soaps and detergents. Fe
and Mn salts impart undesirable colour to the fabric.
Ice making, brewing, canning and distillery industry Free from hardness and bacteria.

Hardness of water

The waters which do not produce lather or produces very little lather with soap are known as hard water. On the other hand soft waters readily produces a lot of lather when mixed with a little of soap. Therefore the study of hardness of water has great importance.

✷Hardness:Hardness was originally defined as the soap consuming capacity of a water sample. Soaps generally consists of the sodium salts of long chain fatty acids such as oleic acid, palmetic acid and stearic acid.The soap consuming capacity of water is mainly due to the presence of calcium and magnesium ions. These ions react with the sodium salts of long chain fatty acids present in the soap to form insoluble scums of calcium and magnesium soaps, which do not possess any detergent value.

`2C_{17}H_{35}COONa+CaCl_2rightarrowleft(C_{17}H_{35}COOright)_2Ca+2NaCl`

Soap (soluble)Calcium soap (insoluble) Other metal ions like `Fe^{+2}`, `Mn^{+2}` and `Al^{+3}` also react with the soap in the same fashion, thus contributing to hardness but generally these are present in natural waters only in traces. Further, acids such as carbonic acid can also cause free fatty acid to separate from soap solution and thus contribute to hardness. However, in practice, the hardness of a water sample is usually taken as a measure of its `Ca^{+2}` and `Mg^{+2}` content.

Degree of Hardness

Hardness of water is never present in the form of calcium carbonate, because it is insoluble in water. Hardness of water is expressed as equivalent of calcium carbonate `CaCo_3`.Degree of hardness is defined as the part of calcium carbonate equivalent hardness per a definite number of parts of water depending upon the units in which hardness is expressed.

Types of Hardness

It is of following two types:

(i) Temporary Hardness:

Temporary hardness is mainly due to the presence of bicarbonate of calcium and magnesium.It is also known as carbonate hardness or alkaline hardness. It can be removed easily be boiling the water. On boiling bicarbonates of calcium and magnesium get decomposed and formed insoluble carbonates or hydroxides which can be removed in the form of precipitates.

CaHCo3→∆CaCo3+H2o+Co2MgHCo32→∆MgOH2+2Co2

(ii) Permanent Hardness:

It is due to the presence of chlorides and sulphates of calcium, magnesium, iron and other heavy metals such as `Al_2(SO_4)_3` etc. It is also known as non-carbonate or non-alkaline hardness. It cannot be removed by simply boiling the water. However it can be removed by using various chemical agents.

Total Hardness = Temporary Hardness + Permanent Hardness

Units of Hardness

Various units used for expressing hardness of water are as under.
1. Parts per million (ppm)
2. Milligrams per liter (mg/L)
3. Degree french (°Fr)
4. Degree Clark (°Cl)

1. Parts per million (ppm)

It is defined as number of parts of calcium carbonate equivalent hardness present per `10^6` parts of water. This is most common unit for expressing the hardness of water.
∴1 ppm = 1 part of `CaCo_3` equivalent hardness of `10^6` parts of `H_2O`

2. Milligrams per litre (mg/L)

It is defined as the number of milligrams of `CaCo_3` equivalent hardness present per litre of water.
∴1 mg/L = 1 mg of `CaCo_3` equivalent per `10^6` mg of water
= 1 part of `CaCo_3` equivalent per `10^6` parts of water
= 1 ppm
Thus, mathematically both the units are euqal.

3. Degree French (°Fr)

It is defined as the number of parts of `CaCo_3` equivalent present per `10^5` parts of water.
∴1°Fr = 1 part of `CaCo_3` equivalent hardness per `10^5` parts of water

4. Degree Clark (°Cl)

It is the number of grains (1/7000 1b) of CaCO3 equivalent present per gallon (10 lbs or 70,000 grains).Always remember that, 1 lb = 7000 grain and one gallon = 70,000 grains.It is defined as the number of parts of `CaCo_3` equivalent hardness present per 70,000 parts of water.
∴1°Cl = 1 parts of `CaCo_3` equivalent hardness per 70,000 parts of water.

Relationship among various units of hardness

1 ppm = 1mg/L = 0.1 °Fr = 0.07°Cl
➤ 1 mg/L = 1ppm = 0.01 °Fr = 0.07°Cl
➤ 1°Cl = 1.433 °F = 14.3ppm = 14.3 mg/l
➤ 1°F = 10ppm = 10 mg/L = 0.7°Cl
The above relation can be derived as follows:
We know that,
➤ 1 ppm = 1 part per 10,00,000 parts of water
➤ 1°Cl = 1 part per 70,000 perts of water
➤ 1°Fr = 1 part per 1,00,000 parts of water
∴ 10,00,000 ppm = 70,000°Cl = 1,00,000°Fr
or 100 ppm = 7°Cl = 10°Fr
or 1ppm = 0.07°Cl = 0.1°Fr

Conclusion

Water is a crucial element in industrial processes, connecting operations, efficiency, and environmental impact. Knowledge of water sources, quality, and hardness is essential for industries to prosper sustainably. Responsible water management practices are necessary for a balance between industrial advancement and environmental conservation.

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