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Application of carbon dioxide in the water purification process

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Water and wastewater treatment processes with carbon dioxide

Water purification is the process of making water suitable for a specific purpose, such as drinking, irrigation, or industrial use. There are various methods of water purification that depend on the source and quality of the water, as well as its intended use. Some common water purification methods include:

Traditional filtration:

This method involves adding chemicals to the water to create larger particles in the form of clumps that can be removed by sedimentation and filtration. This method can remove sand, large bacteria, algae, and some organic matter from the water.

Microfiltration:

This method uses membranes with pore sizes of 0.1 to 10 micrometers to filter suspended solids, dirt, fibers, and colloids from water. This method can improve the clarity and taste of water.

Ultrafiltration:

This method uses membranes with pore sizes of 0.001 to 0.1 micrometers to filter out viruses, humic acids, and some water-soluble organic compounds. This method can improve water quality and safety.

Nanofiltration:

This method uses membranes with pore sizes of 1 to 10 nanometers to remove divalent ions such as calcium, magnesium, and sulfate from water. This method can reduce water hardness and salinity.

Reverse Osmosis:

This method uses membranes with pore diameters less than 1 nanometer to remove monovalent ions such as sodium, chloride, and nitrate from water. This method can purify salty seawater and make it suitable for human consumption.

These are a number of types of water purification processes that can produce water for various applications. Depending on specific needs and standards, various combinations of these methods can be used to achieve the desired results.

Before and after water purification by any of the above methods, additional processes are required to control the pH (acidity or alkalinity) of the water, remove dissolved contaminants, disinfect the water, and ultimately improve its quality.

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Use of carbon dioxide in the water purification process

What gases are used in the water and wastewater treatment process?

In water and wastewater treatment processes, various gases are used to remove dissolved contaminants, disinfect water, and improve its quality. Some of the gases commonly used in these processes include:

1. Chlorine:

Chlorine is a strong oxidizing agent used to kill microorganisms and oxidize organic and inorganic compounds. Chlorine is usually added to water in the form of sodium hypochlorite or as a gas. This gas can react with ammonia to produce chloramines, which are more stable and less corrosive than chlorine itself.

2. Ozone:

Ozone is also a very strong oxidizing agent used to destroy microorganisms, organic pollutants, and flavor and odor compounds. The gas is produced by electrical discharge or ultraviolet radiation. Ozone is often combined with processes such as filtration or bioremediation to improve its effectiveness.

3. Carbon dioxide:

Carbon dioxide is a weak acid that can lower the pH of water and increase its solubility. This gas is used to adjust the pH of water after treatment with alkaline substances such as lime or soda to increase the pH and facilitate the precipitation of substances. Carbon dioxide can also be effective in processes of reducing suspended particles and improving water quality.

Ammonia:

Ammonia is a weak base that can raise the pH of water and act as a nutrient for biological processes. Ammonia is commonly added to water to react with chlorine to produce chloramines. It is a potent disinfectant that can improve water disinfection performance while reducing the formation of undesirable byproducts. Ammonia can also be effective in removing iron and manganese from water.

These are just some of the gases commonly found in water and wastewater treatment processes. In some situations, other gases such as methane, hydrogen sulfide, or carbon monoxide may also be produced or released during water treatment. These gases may pose health and safety risks to humans and should be carefully monitored.

Carbon dioxide (CO₂) has various applications in water and wastewater treatment processes that help improve water quality, reduce pollutants, and optimize treatment processes. Some of its applications include:

Neutralization (lowering pH):

Carbon dioxide can be used to lower the pH of alkaline wastewaters that may contain ammonia, phosphate, or bicarbonate. CO₂ reacts with water to produce carbonic acid, a weak acid that can neutralize these alkaline compounds. Using CO₂ in this process is safer than using mineral acids such as sulfuric and hydrochloric acid, which are corrosive and dangerous. CO₂ can also prevent the formation of deposits and rust in pipes and equipment.

Mineral recovery and water hardness adjustment:

Carbon dioxide can be used to increase the hardness and alkalinity of soft or mineralized water that may be unstable. CO₂ reacts with calcium hydroxide (CaOH) to produce calcium carbonate and water. Calcium carbonate is a naturally occurring mineral that can help stabilize water quality and prevent rusting. In addition, CO₂ can improve coagulation and flocculation processes by adjusting pH and particle load.

Carbon dioxide capture (reduction of gaseous pollutants):

Carbon dioxide can be used to capture CO₂ from polluting gases such as soot or biogas, which are emitted as greenhouse gases from wastewater treatment plants. By injecting CO₂ into wastewater, stable mineral carbonates and bicarbonates are formed, which can be precipitated as valuable products. These products can be used in the construction industry or as chemical buffers in water treatment cycles or in reducing ocean acidity.

Carbon dioxide injection (acidity reduction and metal removal):

In this process, carbon dioxide is injected into the water to lower its pH and increase its acidity. This can help remove hardness, iron, manganese, and other metals from the water, as these metals precipitate as cyclic bicarbonates. Carbon dioxide injection can also prevent carbonate deposits from forming in pipes and equipment. This process is often combined with softeners such as lime or soda ash, ion exchange, or reverse osmosis.

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Carbon dioxide gas extraction:

This process refers to the removal of carbon dioxide from water by exposing it to air or another gas. During this process, carbon dioxide is separated from the water solution and released into the atmosphere. Carbon dioxide degassing can help increase the pH of the water and reduce its acidity, which ultimately improves water quality and maintains its chemical balance.

This process is particularly effective in preventing corrosion of pipes and equipment, as reducing the concentration of carbonic acid, which is formed when carbon dioxide combines with water, can prevent damage from corrosion. CO₂ degassing can also be effective in other water treatment processes, such as removing heavy metals and adjusting water hardness.

This process is often used as a complementary step in water treatment, especially in processes that require precise pH.

Where can we get carbon dioxide gas?

According to the requirements specified in the previous paragraphs, industrial centers must obtain their required carbon dioxide only from reputable carbon dioxide gas production centers.

Carbon dioxide gas and liquid in these centers are constantly subjected to purity tests for each batch produced, and its characteristics and impurities are constantly measured.

Sial Tamin Roham Company is a supplier of liquid carbon dioxide with appropriate purity for industrial applications, used in water and wastewater treatment processes, carbon dioxide storage and transportation tanks, carbon dioxide gas cylinders and bundle pallets, as well as a supplier of related equipment, including high-pressure regulators, special carbon dioxide gas hoses, and other equipment for industrial centers.

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