Water is essential for the life and health of living things, but unfortunately, not all water sources are safe for direct consumption. The presence of pathogenic microorganisms and contaminants can put the health of people who drink or use untreated water at risk.
This is a more widespread problem than it may seem: According to data from the World Health Organization and UNICEF, in 2021 29% of the world’s population did not have access to a safe source of drinking water.
Luckily, there are various techniques for purifying water, and one of the most used and effective is treatment with sodium hypochlorite.
What is sodium hypochlorite?
Sodium hypochlorite is a chemical solution obtained through the reaction of chlorine gas with sodium hydroxide. It is commonly known as “liquid chlorine” and is widely used as a disinfectant and bleaching agent due to its ability to kill bacteria, viruses, algae, and other pathogenic microorganisms present in water.
It is produced by the reaction of chlorine gas (Cl2) with sodium hydroxide (NaOH) or sodium carbonate (Na2CO3). This reaction produces sodium hypochlorite along with sodium chloride and water: Cl2 + 2 NaOH → NaClO + NaCl + H2O
Sodium hypochlorite comes in liquid form, with a concentration of active chlorine that can vary, generally expressed as a percentage of available chlorine. One of its most widely used applications is to disinfect and purify water, either by making it safe for human consumption, as well as in the sanitation of swimming pools, treating wastewater, and disinfection of surfaces and equipment.
The use of sodium hypochlorite in water treatment
Sodium hypochlorite water treatment is one of the most effective and economical ways to purify water on a large scale. Disinfection processes with sodium hypochlorite can be carried out in different stages:
- Pretreatment: Before sodium hypochlorite is added, the water is pre-treated to remove large particles and sediment through filtration or sedimentation processes.
- Dosage: The sodium hypochlorite is dosed in the water in an adequate quantity to guarantee effective disinfection, but without exceeding the permitted limits of residual chlorine.
- Contact time: It is important that the sodium hypochlorite have sufficient contact time with the water to kill harmful microorganisms. The contact time may vary depending on the chlorine concentration and the characteristics of the water.
- Neutralization: After disinfection, neutralization is carried out to eliminate excess residual chlorine before distributing drinking water to the population.
Advantages of water treatment with sodium hypochlorite
Sodium hypochlorite water treatment offers several advantages, which explains why it is a widely used and effective option for water disinfection and purification:
- It is highly effective against pathogenic microorganisms: Sodium hypochlorite is a powerful disinfectant that has the ability to kill a wide range of pathogenic microorganisms present in water, including bacteria, viruses, parasites, and algae. This ensures that the treated water is safe for human consumption and the protection of public health.
- Wide availability: Sodium hypochlorite is easily accessible on the market and is available in liquid form in different concentrations. This facilitates its use in water treatment plants of different sizes and capacities.
- An Effective cost: Compared to other disinfection technologies, sodium hypochlorite is a more economical and cost-effective option for large-scale water treatment. This is especially important in areas where financial resources are limited.
- Ease of application: Its liquid presentation allows a simple and precise dosage in water treatment processes. Furthermore, it can be applied to different stages of the treatment process based on specific needs.
- Fast action time: Sodium hypochlorite acts rapidly in the elimination of microorganisms, which allows effective disinfection in a relatively short time.
- Destruction of unpleasant odors and flavors: In addition to disinfecting water, sodium hypochlorite can help reduce unpleasant tastes and odors associated with some contaminants in water.
- Safety with proper dosage: When used correctly and dosed in a controlled manner, sodium hypochlorite is safe and effective. Additionally, it breaks down into less toxic substances, such as salt and water, during the disinfection process.
- Compatibility with other treatment systems: Sodium hypochlorite can be combined with other treatment technologies, such as filtration, to obtain optimal results in water purification.
- Control of epidemics and health emergencies: Sodium hypochlorite is a valuable tool for controlling the spread of waterborne diseases in emergencies and health crises.
Risks of water treatment with sodium hypochlorite
Sodium hypochlorite water treatment is a safe and efficient option to guarantee the supply of drinking water. However, itmayhave some drawbacks, for example:
- Sodium hypochlorite water treatment can create a residual chlorine taste and odor in the water, which may be unpleasant to some people. . This problem can be minimized with proper dosage and contact time
- During the sodium hypochlorite disinfection process, undesirable chemical by-products such as trihalomethanes (THMs) and chloramines can be formed.
- It is a relatively unstable substance and can degrade over time, especially under conditions of high temperatures or exposure to strong sunlight. Also, being a corrosive chemical substance, it can cause skin and eye irritation if handled improperly.
Despite these disadvantages, it is important to note that sodium hypochlorite water treatment remains an effective and widely used option for large-scale water disinfection because, as we have indicated, the advantages outweigh the aforementioned disadvantages, as long as proper dosing and safety protocols are followed.
After all, access to drinking water not only has a great impact on people’s health and lives, but also on an economic and social level.
