Comparison between sodium hypochlorite and hypochlorous acid in process water disinfection

Sodium hypochlorite is a common disinfectant that may already be familiar to you. It is also used in process water in various industries, such as the food and chemical industries. Although this agent can be effective, its use comes with drawbacks. In this article, we will discuss the properties of sodium hypochlorite, its disadvantages and a possible alternative: hypochlorous acid.

What is sodium hypochlorite?

Sodium hypochlorite is a disinfectant commonly used for water and surface disinfection. It is created by a chemical reaction between chlorine and sodium hydroxide. Many bleaches contain this active ingredient. Well-known uses of sodium hypochlorite are in toilets or swimming pools. In households, this agent is often called “thick bleach” [1]. In factories, it is used to disinfect process water, although this has some drawbacks.

Disadvantages of sodium hypochlorite

Sodium hypochlorite is associated with health hazards and, depending on the application, can be counted among the CMR substances. It can cause burns or skin irritation upon skin contact and serious eye damage upon eye contact. Regular exposure can cause respiratory infections and symptoms of asthma [2]. In addition, sodium hypochlorite often leads to the formation of disinfection byproducts, such as trihalomethanes, which are potentially harmful to health and the environment [3].

Sodium hypochlorite in process water

Sodium hypochlorite is also used in various industrial applications [4]. Some sectors where it is applied include the chemical, dairy, food, and glue industries. It is used for water treatment and algae prevention in cooling towers, among others. In the food and beverage industry, sodium hypochlorite is sometimes used in cleaning-in-place (CIP) processes, where it serves as a disinfectant during the post-rinse phase [5].

Water quality process water

Water quality of process water is critical for all industries. Water that comes into contact with a product can compromise the quality of the final product if contaminated. This can pose risks to the end user and reduce the product's shelf life. For these reasons, it is necessary to use a disinfectant that poses as little (health) risk as possible. One possible alternative is hypochlorous acid.

What is hypochlorous acid?

Hypochlorous acid (HOCl) is commonly used as a disinfectant and is produced using a technique called electrochemical activation (ECA). In this process, a saltwater solution is electrolyzed, producing a disinfectant suitable for various applications. HOCl is also produced by the human body and plays a role in the immune system as part of the defense against microorganisms. It has bactericidal and virucidal activity, meaning it can kill bacteria, fungi, yeasts, and viruses [6].

HOCl in process water

HOCl can be used for various process water aplications, such as in cooling water, rinse water, CIP, water used for product transportation, and as an ingredient in products. When using an ECA system, a disinfectant containing HOCl can be produced on site (in-situ). This agent effectively eliminates microbiological contamination and prevents biofilm growth. Because the required dosage of HOCl can be very low, the likelihood of unwanted residues, such as chlorate, is extremely low [7].

References:

1. Waarzitwatin.nl. Bleek.
2. Waarzitwatin.nl. Natriumhypochloriet.
3. Richardson, S. D., et al. (2007). Disinfection By-products: Formation, Analysis, and Control. Environmental Science & Technology.
4. Chemicals.co.uk. What is Sodium Hypochlorite Used For?
5. MDPI. (2021). Cleaning-in-place systems in food processing: Guidelines and evaluation. Beschikbaar op MDPI.
6. Park, S., et al. (2019). Electrochemically Activated Water in Food Processing. Trends in Food Science & Technology.
7. MDPI. (2021). Application of HOCl for Process Water Treatment. Beschikbaar op MDPI.