Residual chlorine analyzer is to ensure the disinfection effect in food and beverage factories

In the water treatment of food and beverage factories, chlorination disinfection is the key link to kill pathogenic bacteria, viruses and microorganisms in water, and the residual chlorine analyzer is the core monitoring equipment to ensure the disinfection effect and avoid excessive/low residual chlorine. Its function is to monitor the concentration of "residual chlorine" (chlorine with bactericidal ability remaining after disinfection, including free residual chlorine and combined residual chlorine) in water in real time, so as to accurately control the amount of chlorine added. The following is based on the special needs of food and beverage factories to analyze the application value, adaptation scenarios and precautions of residual chlorine analyzer in chlorination disinfection control:

I. Special requirements of food and beverage factories for residual chlorine control

The production water of food and beverages (such as raw water, cleaning water, cooling water) directly or indirectly contacts the product, and has extremely strict requirements on microbial indicators (such as total colony count, Escherichia coli) (such as GB 19298-2014 "Packaged Drinking Water" requires total colony count ≤100 CFU/mL, and pathogenic bacteria shall not be detected).

The core contradiction of chlorination disinfection is:

•  Insufficient residual chlorine: unable to completely kill microorganisms, there is a risk of product contamination (such as spoilage of beverages, excessive food colonies);
• Excessive residual chlorine: produces chlorine and irritating odors, affecting the flavor of food/beverages (such as bottled water with a "bleaching smell"); it may also react with organic matter in water to produce disinfection by-products (DBPs) such as chloroform, which endangers human health and violates food safety standards.

Therefore, residual chlorine needs to be strictly controlled in the "effective sterilization without adverse effects" range  (usually:

• Beverage raw water: free residual chlorine 0.05-0.3 mg/L;
• Washing water: free residual chlorine 0.5-1.0 mg/L, to avoid residues after washing;
• Cooling water: combined residual chlorine 1.0-3.0 mg/L, to reduce corrosion to equipment).
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II. The core role of residual chlorine analyzer in chlorination disinfection control

The residual chlorine analyzer provides a "feedback signal" for the chlorination system by real-time monitoring of the residual chlorine concentration in the water, achieving precise control. The specific functions are as follows:

1.Ensure disinfection effect and eliminate microbial risks

The online residual chlorine analyzer can track the residual chlorine concentration in real time (the response time is usually <30 seconds). When the residual chlorine is lower than the target value, the chlorination pump is automatically linked to increase the dosage (such as chlorine, sodium hypochlorite) to ensure that the microorganisms are continuously killed. For example: before the raw water enters the storage tank, if the residual chlorine drops from 0.2 mg/L to 0.03 mg/L, the analyzer will immediately alarm and trigger chlorination to prevent substandard water from entering the production process.

2.Avoid excessive residual chlorine and protect product quality

When the residual chlorine exceeds the set upper limit (such as beverage water> 0.3 mg/L), the analyzer will send a signal to reduce the amount of chlorine to prevent the chlorine smell from affecting the product flavor. For example: in the production of bottled water, excessive residual chlorine will cause the product to have a "astringent taste" and increase the consumer complaint rate. The analyzer can stably control the residual chlorine at 0.1-0.2 mg/L, taking into account both sterilization and taste.

3.Reduce operating costs and reduce waste of reagents

Traditional manual testing (such as timed sampling and colorimetric analysis with DPD reagent) has lags and is prone to overdosing. The closed-loop control of the residual chlorine analyzer can accurately match actual needs (such as automatically reducing chlorine addition when the raw water microbial load is low). According to statistics, it can reduce disinfectant consumption by 10-20%, especially for large beverage plants (daily water consumption of thousands of tons), with significant long-term economic benefits.

4.Meet compliance requirements and facilitate traceability

The food and beverage industry is strictly regulated (such as ISO 22000, HACCP system), and water quality monitoring data needs to be recorded. The residual chlorine analyzer can automatically store historical data (such as recording once every 10 seconds) and generate trend reports to facilitate verification by regulatory authorities and avoid compliance risks caused by "incomplete disinfection records".

III. Comparison of the applicability of different types of residual chlorine analyzers

According to the principle, the residual chlorine analyzer can be divided into colorimetric method and electrode method. The two methods are suitable for different scenarios in food and beverage factories and need to be selected according to the characteristics of water quality: