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

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Introduction

Undoubtedly, water is essential for life and, moreover, simultaneously plays a vital role in a wide range of industrial activities. Furthermore, specifically in industrial contexts, its quality and properties consistently serve as key factors in determining both efficiency and environmental impact in processes such as manufacturing and energy production. Consequently, understanding water’s role becomes crucial in optimizing industrial performance and, therefore, ensuring long-term sustainability. In this context, additionally, this blog will explore the influence of water, trace its origins, and highlight the significance of water hardness in various industrial environments.

Water splash forming a circle with the text "Water and Its Industrial Applications" inside, set against a clear blue sky and sea background.

Water is the basic necessitiy of life. It is necessary for the survival of all livings. Surprisingly and in fact, water covers approximately 80% of the Earth’s surface. Nevertheless and even so, despite this vast coverage, only 1% of the total water remains readily available. Consequently and accordingly, this limited portion must support various uses, including domestic, agricultural, municipal, and industrial work. Therefore and hence, efficient management becomes essential.

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
Flowchart showing sources of water: surface (streams, rivers, ponds, lakes), underground (springs, wells), rain, and estuarine/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

To begin with, finely divided clay and silica both contribute significantly to water turbidity. Moreover, aluminium hydroxide and ferric hydroxide actively participate in coagulation and flocculation processes. In addition, organic waste products and humic acids introduce natural organic matter that can affect taste and odor. Furthermore, colouring matter and complex proteins further influence water’s visual and organoleptic properties. Lastly, amino acids—which generally classify as albunoid ammonia—also play a role in nutrient dynamics and biological activity within the water.

(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:Originally, hardness was defined as the soap-consuming capacity of a water sample. This is because soaps generally consist of the sodium salts of long-chain fatty acids, such as oleic acid, palmitic acid, and stearic acid. In most cases, the soap-consuming capacity of water is mainly due to the presence of calcium and magnesium ions. Specifically, 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, in turn, do not possess any detergent value. Therefore, water containing these ions is considered hard, as it reduces the effectiveness of soap.

`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:

To begin with, temporary hardness arises from the presence of calcium and magnesium bicarbonates. As a matter of fact, people commonly refer to it as carbonate hardness or alkaline hardness. In addition, this type of hardness disappears when one boils the water. When heated, calcium and magnesium bicarbonates break down into insoluble carbonates or hydroxides. As a result, these compounds form precipitates. After that, one can remove the solids through filtration. Therefore, treating temporary hardness is relatively simple compared to permanent hardness. In conclusion, understanding this process helps in selecting the correct water softening method.Ultimately, understanding this process helps in choosing the appropriate water softening method.

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

(ii) Permanent Hardness:

Specifically, this type of hardness occurs due to the presence of chlorides and sulphates of calcium, magnesium, iron, and other heavy metals such as Al₂(SO₄)₃. Consequently, it is also known as non-carbonate or non-alkaline hardness. In contrast, one cannot remove it by simply boiling the water, unlike temporary hardness. However, various chemical agents can effectively eliminate it.

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)

To begin with, we express water hardness in terms of the number of grains—where one grain equals 1/7000 of a pound—of calcium carbonate (CaCO₃) equivalent present per gallon of water. Subsequently, we note that one gallon of water weighs approximately 10 pounds, or 70,000 grains. Accordingly, we define one grain per gallon (gpg) as one part of CaCO₃ equivalent hardness in 70,000 parts of water by weight. As a result, this definition allows a clear comparison of different water samples. Moreover, it ensures consistent classification of water hardness levels across various regions.
∴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

Clearly, water is a crucial element in industrial processes, as it directly connects operations, efficiency, and environmental impact. In this regard, knowledge of water sources, quality, and hardness is essential for industries to prosper sustainably. Therefore, responsible water management practices are necessary to ensure a balance between industrial advancement and environmental conservation.

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