Classification of Impurities Present in Water Related to Industrial Application


Water plays a crucial role in various industrial applications. However, it is often contaminated with impurities thWater Treatment Methodsat can adversely affect the efficiency and quality of these processes. This article aims to classify and explain different impurities found in water, outlining their effects on industrial applications and their method of removal.

Classification of Impurities Present in Water

The impurities present in water can be broadly classified into three categories.

1) Non-ionic impurities (or) undissolved impurities
2) Ionic impurities (or) dissolved impurities
3) Gaseous impurities

Non-Ionic Impurities in Water

When it comes to water used by industries, it is crucial to acknowledge the presence of non-ionic impurities that may have an unfavorable impact on both the environment and human health. These impurities can originate from various sources, including natural occurrences and industrial activities.
Major non-ionic impurities are as follows

1) Turbidity or suspended solids.
2) Colour
3) Taste and odor
4) Organic matter
5) Colloidal silica
6) Microorganism
7) Oil.

1) Turbidity or Suspended Solids:

Turbidity refers to the cloudiness of water caused by the presence of suspended particles. These particles can include sediment, clay, silt, organic matter, algae, and precipitated iron. High levels of turbidity can pose several challenges for industries as it can interfere with processes such as filtration, disinfection, and the clarity of end products. Industries must employ effective filtration systems to remove suspended solids and ensure water quality.

2) Colour:

Water color is usually expressed in Hazen units and is caused by the presence of aquatic growth or colloidal suspension. Color in water is usually caused by the presence of dissolved organic and inorganic compounds. Organic compounds derived from decaying vegetation or industrial effluents can give water an undesirable color. Sometimes water may have color due to the presence of iron.

3) Taste and Odour:

Water impurities can also contribute to changes in taste and odour. These sensory aspects are often associated with the presence of volatile organic compounds (VOCs) and chemical contaminants. These chemicals can be created from municipal or industrial waste or natural resources such as the decomposition of plant matter. Industries that rely on water for food and beverage production or pharmaceutical manufacturing must ensure that the water used in their processes is free from any unpleasant taste or odor to maintain the quality of their products.

4) Organic Matter:

The presence of organic matter in water can result from natural sources (e.g., decaying plants and animals), human savage matter or its degradation products, industrial waste, and agricultural pesticides and herbicides. This can include a variety of substances, such as bacteria, algae, and humic acids. High levels of organic matter can promote bacterial growth, which can lead to microbial contamination and hinder industrial processes that require sterile or clean water.

5) Colloidal Silica:

Colloidal silica particles are small suspended particles ranging in size from 0.001 to 1 micron. These impurities are commonly found in industrial water supplies, particularly in silica-rich areas. Colloidal silica can be challenging to remove and can cause scaling or fouling issues in heat exchangers and other equipment. Industries must employ effective filtration techniques to eliminate or reduce colloidal silica from water sources.

6) Microorganism:

Microorganisms are usually not present in deep well water but are moderately common in surface water. Microorganisms are offensive in water because they are sources of disease and slime formation.

7) Oil:

In industries where oils are widely used or produced, the presence of oil in water becomes a pertinent concern. Oil can contaminate water sources through spills, leaks, or improper disposal practices. The presence of oil can have severe environmental consequences and disrupt various industrial processes. Stringent measures must be in place to prevent oil contamination and provide appropriate treatment methods if incidents occur.

Ionic Impurities (or) Dissolved impurities

Ionic impurities are further subdivided into Cationic and Anionic impurities.

Major cationic impurities

Cationic impurities play a significant role. These are positively charged ions that can have both beneficial and detrimental effects on water quality. Let’s explore the major cationic impurities step by step:

1) Calcium & Magnesium
2) Sodium
3) Potassium
4) Iron
5) Manganese
6) Aluminum

1) Calcium (Ca2+) & Magnesium (Mg2+):

Calcium and magnesium are the most common cations-dissolved impurities found in water. It can originate from natural sources like rocks and minerals or be introduced through industrial processes. While calcium and magnesium salts are essential minerals for human health, high levels of calcium and magnesium salts in water can lead to water hardness, causing scaling in pipes, boilers, and appliances. The calcium and magnesium salts are causes hardness and divided into two types.

a) Carbonate or temporary hardness.
b) Non-carbonate or permanent hardness.

Proper treatment and control of Calcium (Ca2+) & Magnesium (Mg2+) levels are necessary for optimizing water quality.

3) Sodium (Na+):

Sodium is a cationic impurity in soluble elements, and it is present in most natural waters. The range of sodium levels can be from one ppm to several thousand ppm as in brine or sea water. Sodium primarily enters water sources through natural means or industrial activities like distillation processes. While low levels of sodium are generally acceptable in drinking water, high concentrations can be problematic for individuals on sodium-restricted diets or those with health conditions like hypertension. Being alkaline in nature, they can accelerate the corrosion of pipes, boiler tubes, and appliances in industries.

4) Potassium (K+):

Potassium is a cationic impurity that can enter water sources naturally or due to agricultural practices. Unlike other cations, potassium is typically not a concern in terms of water quality. In fact, moderate levels of potassium can be beneficial, as it is an essential nutrient for plants and humans. However, excessively high levels of potassium can impact the taste of water and create potential health risks.

5) Iron (Fe2+/Fe3+) and Manganese (Mn2+):

Iron and Manganese are cationic impurities that can be present in water due to geological formations, corrosion of iron pipes, or industrial processes.

Iron can be found in water supplies as follows:

a) Dissolved iron
b) Precipitated iron: oxidized iron, both filterable and colloidal.
c) Organic bound iron.
d) Components of living organisms (Iron bacteria)

In surface and groundwater supplies, iron commonly exists as divalent ferrous salts or as organic complexes. Manganese with a few exceptions, exists as divalent manganese. While low levels of iron and manganese are considered safe, high concentrations can cause aesthetic issues, such as colored water and staining of fittings. They can also cause clogging of pipelines in industrial applications. Monitoring and treatment methods are essential to maintaining acceptable Iron and manganese levels in water.

6) Aluminum (Al3+):

Aluminum is a cationic impurity that can enter water sources through natural means or human activities such as mining and industrial processes. While low levels of aluminum are typically considered safe, elevated levels can be toxic and harmful to human health. Proper management and treatment are necessary to prevent excessive aluminum concentrations in water.

Major anionic impurities

1) Bicarbonates
2) Carbonates
3) Hydroxide
4) Fluorides
5) Chlorides
6) Sulphates
7) Nitrates
8) Phosphates
9) Silica.

1) Bicarbonates (HCO3-):

Bicarbonates are anionic impurities commonly found in water. They are formed by the presence of dissolved carbon dioxide (CO2) in water. CO2 (Carbon dioxide) reacts with water to form carbonic acid (H2CO3), which then separates into bicarbonate ions. Bicarbonates can contribute to water hardness and affect the pH levels of water.

2) Carbonates (CO32-):

Carbonates represent a type of anionic impurity commonly encountered in water sources. They originate from the separation of carbonic acid (H2CO3) or other carbonate compounds naturally present in water. These carbonate impurities can contribute to water hardness and exert an influence on pH levels.

3) Hydroxide (OH):

Hydroxide ions are generated during the dissociation of water molecules, resulting in the release of hydroxide ions into the solution. Hydroxide impurities can enter water supplies through various industrial processes, such as metal plating or the production of detergents. High concentrations of hydroxide ions have the possibility to elevate the alkalinity of the water.

4) Fluorides (F):

Fluoride impurities can be naturally occurring in water or added through fluoridation programs aimed at promoting dental health. However, excessive fluoride concentrations in water can lead to dental and bone fluorosis, causing health issues. Proper monitoring and control are necessary to maintain optimum levels of fluoride in water.

5) Chlorides (Cl):

Chloride ions are commonly found in water sources, particularly in areas near the coast or where saltwater intrusion occurs. Industrial activities such as chemical production and wastewater discharge can introduce chloride impurities into water. High concentrations of chloride ions can impact the taste and quality of water and cause corrosion of pipes and infrastructure in industries.

6) Sulphates (SO42-):

Sulphate impurities are often present in water due to the weathering of rocks and minerals. They can also result from industrial activities such as mining and chemical production. High levels of sulphate ions can cause aesthetic issues like bitter taste and laxative effects. Furthermore, sulphates can react with certain chemicals to form sulfide compounds, which can lead to foul odors.

7) Nitrates (NO3-):

Nitrates are commonly found in water due to agricultural practices like the use of fertilizers and animal waste runoff. High levels of nitrate impurities can be harmful, particularly for infants. Monitoring and control of nitrate levels are essential for ensuring the safety of drinking water.

8) Phosphates (PO43-):

Phosphate impurities can enter water sources through agricultural runoff, detergents, and industrial discharges. Excessive phosphate levels in water can lead to eutrophication, causing the growth of harmful algal blooms, oxygen depletion, and disruptions in aquatic ecosystems.

9) Silica (SiO2):

Silica impurities are commonly found in natural water sources due to the weathering of rocks and minerals. High levels of silica can cause scaling in boilers and other industrial equipment, reducing their efficiency and lifespan.

Gaseous impurities

Gaseous impurities can have a significant impact on the quality of water. Industries can release these gases into water sources through various processes, such as the discharge of effluents or accidental chemical spills. Contaminated water containing high levels of these gaseous impurities can be hazardous to both the environment and human health.

Some common gaseous impurities found in water are as follows:

Carbon dioxide
Hydrogen sulfide

1) Carbon Dioxide (CO2):

Carbon dioxide is a naturally occurring gas that dissolves in water, forming carbonic acid. This impurity is often present in water due to natural processes as well as human activities such as combustion and industrial emissions. Although carbon dioxide itself is not usually considered harmful, high concentrations of dissolved carbon dioxide can lead to water acidification, which can affect aquatic life and alter the pH balance of the water.

2) Hydrogen Sulfide (H2S):

Hydrogen sulfide is a colorless and toxic gas found in water. It comes from decaying stuff and industrial activities like mining and drilling. Too much of it in water can make people sick with nausea, headaches, and breathing problems. It can also damage pipes and make water taste and smell bad.

3) Ammonia (NH3):

Ammonia is a mix of nitrogen and hydrogen. It can get into water from nature, like when things rot, or from farming when fertilizers are used. In industries, ammonia is used in making stuff. Too much ammonia in water is bad for fish and can lower the oxygen in water, which is bad for them. It can also be harmful to people if they drink water with too much ammonia.

4) Oxygen (O2):

While oxygen is essential for sustaining life, it can sometimes be considered an impurity when present in high concentrations in water. This can occur due to excessive aeration or turbulence in water bodies. High oxygen levels can lead to imbalances in aquatic ecosystems, affecting the survival of certain organisms. However, it is important to note that oxygen is typically not considered a harmful impurity unless present at extreme levels.

Understanding Water Impurities in Industrial Processes: effects on Industrial environment and a basic idea of the removal method.

Major non-ionic impurities

Impurities Effect

Method of Removal

pH Low and high pH levels can both induce corrosion. This means that if the pH of the water is too low or too high, it can lead to damage or deterioration of materials in contact with the water. a) Ion exchange process: This method involves exchanging ions in the water with ions on a solid resin. This can help stabilize and regulate the pH level. b) Addition of acid or alkali: Adding specific chemicals, such as acids or alkalis, can be used to adjust and bring the pH level to an optimal range.
Turbidity Turbidity refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles. In water, high turbidity can clog pipelines and equipment, reducing their efficiency and potentially causing damage. a) Coagulation process: This involves adding chemicals that cause particles to clump together, making them easier to remove.
Suspended Silica Suspended silica particles can choke Ion Exchange Resin (IER) and Reverse Osmosis (RO) membranes, leading to a decrease in their effectiveness and efficiency. a) Sedimentation and Filtration process: This involves allowing the particles to settle out and then using filters to remove them from the water.
Color Color in water can indicate the presence of various impurities such as organic matter or iron. It can also be harmful to unit operations, potentially affecting their performance and efficiency. a) Coagulation process: This is used to agglomerate and settle out colored particles from the water. b) Sedimentation and Filtration process followed by activated carbon filter: This two-step process first removes larger particles through sedimentation and filtration, then further purifies the water using activated carbon.

Ionic or dissolved impurities (Major Cationic and Anionic impurities)

Impurities Effect Method of Removal
Calcium, Magnesium (Hardness) Causes scaling and scum buildup with soap, interfering with dyeing and other processes. a) Ion exchange process: Removing calcium and magnesium ions using ion exchange resins. b) Lime softening process: Precipitating calcium and magnesium ions using lime.
Sodium Low concentrations are not harmful. High concentrations increase TDS and can induce corrosion. a) Ion Exchange through cation H+ resin: Exchanging sodium ions for hydrogen ions. b) Reverse Osmosis: Removing sodium and other ions through a semipermeable membrane.
Iron Causes corrosion and deposits on equipment, leads to red-colored water, and interferes with processes like dyeing and bleaching. a) Aeration Process: Oxidizing iron for removal. b) Coagulation and Flocculation process: Aggregating and removing iron particles. c) Filtration through Manganese Zeolite: Filtering out iron using manganese zeolite media.
Bicarbonates, Carbonates, Alkalinity, Hydroxide (Alkalinity) Causes corrosion in pipes and foaming with carry-over in boilers. a) Acid addition: Neutralizing alkalinity with acids. b) Ion Exchange by weak acid cation resin: Exchanging ions to reduce alkalinity. c) Split stream by hydrogen cation resin: Further ion exchange to reduce alkalinity. d) De-gasification after steps b & c: Removing gases associated with alkalinity.
Sulphate Causes scaling, especially when associated with calcium, and can be harmful in construction water. a) Ion Exchange: Removing sulfate ions using ion exchange resins. b) Reverse Osmosis: Removing sulfate ions through a semipermeable membrane. c) Evaporation: Concentrating water to precipitate sulfate. d) Electrolysis: Removing sulfate through electrochemical processes.
Chloride Causes corrosion in equipment. a) Ion Exchange: Removing chloride ions using ion exchange resins. b) Reverse Osmosis: Removing chloride ions through a semipermeable membrane. c) Evaporation: Concentrating water to precipitate chloride. d) Electrolysis: Removing chloride through electrochemical processes.
Nitrate Usually not found in raw water but can be harmful in food processing. a) Ion Exchange process: Removing nitrates using ion exchange resins. b) Reverse Osmosis process: Removing nitrates through a semipermeable membrane.
Silica Causes deposition and scaling on equipment. Ion Exchange process: Removing silica ions using ion exchange resins.
Free Chlorine Causes corrosion of equipment. a) By adding chemicals: Neutralizing or removing free chlorine. b) Activated carbon process: Adsorbing free chlorine on activated carbon.

Gaseous impurities

Impurities Effect Method of Removal
Carbon Dioxide (CO2) Carbon dioxide (CO2) can lead to corrosion of equipment. a) Aeration Process: This involves exposing the water to air to allow CO2 to escape. b) Degasification: A process that removes dissolved gases, including CO2, from water. c) Vacuum Deaeration: This method uses a vacuum to remove gases from the water.
Hydrogen Sulphide Hydrogen sulphide (H2S) can cause corrosion of equipment. a) Aeration Process: Exposing water to air to allow H2S to escape. b) Filtration through Manganese Zeolite: A method that uses specialized media to remove H2S. c) Aeration followed by chlorination: Combining aeration with chlorination to remove H2S.
Oxygen Oxygen can also lead to corrosion of equipment. a) Deaeration: Removing oxygen from water. b) Addition of chemicals like sodium sulphite or hydrazine: These chemicals react with and remove oxygen. c) Anion exchanger: Using an ion exchange process to remove oxygen ions.
Ammonia Ammonia can cause corrosion, especially of copper and zinc materials. a) Aeration process: Aeration can help remove ammonia. b) Hydrogenation exchange if ammonia is present in ionic form: Using an exchange process to remove ammonia ions.


Summary: Discover the various impurities that can contaminate water used in industrial applications. This comprehensive guide covers non-ionic, ionic, and gaseous impurities, their effects on industrial processes, and effective methods for their removal. Ensure water quality for optimal industrial efficiency.

This comprehensive guide covers non-ionic, ionic, and gaseous impurities, their effects on industrial processes, and effective methods for their removal. Ensure water quality for optimal industrial efficiency.

Thank you for reading this article on water impurities-related industrial processes. We hope you found it an informative and valuable article. If you have any comments, questions, or suggestions, please feel free to leave them below.

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