At present, the safety of drinking water has attracted much attention. Chlorine dioxide has become a hot choice in the field of water treatment because of its high-efficiency sterilization. As a practitioner in the drinking water market, are you also thinking about how to control the residue after chlorine dioxide disinfection? What is the operation process to ensure safety compliance? This article will combine the national standards and industry practice to deeply analyze the comprehensive technology and problem interpretation of chlorine dioxide on drinking water disinfection.

Chlorine dioxide disinfection: technical core and industry advantages

With its powerful oxidation capacity, chlorine dioxide (clo‹) can quickly destroy the cell structure of microorganisms and become an efficient guardian in the field of water treatment. It can kill bacteria, viruses and even stubborn spores. Compared with traditional disinfection methods, chlorine dioxide shows obvious advantages:

1. no chlorination risk: during the disinfection process, it will not react with organic substances in the water to produce substances with carcinogenic risk such as chloroform, which will protect the water quality safety from the source.

2. sustained bacteriostasis: according to gb5749-2022 sanitary standard for drinking water, as long as the residual chlorine dioxide at the end of the pipe network is maintained at more than 0.02mg/l, the secondary reproduction of microorganisms can be effectively inhibited and the water quality can be sustainable and safe.

3. wide application range: whether it is a complex water source with high turbidity and high organic content, or a relatively clean water source with low pollution, chlorine dioxide can easily play a role in disinfection.

After a large-scale municipal water supply project was disinfected with chlorine dioxide, the content of chloroform in the water decreased from the original 0.08mg/l to an undetectable level, and the residual chlorine at the end of the pipe network remained stable at 0.05mg/l, effectively ensuring the water safety of urban residents.

Deep analysis of chlorine dioxide residue

Inevitability of residues

1. demand for continuous disinfection: the national standard gb5749-2022 clearly stipulates that the end water of the pipe network must maintain a residual chlorine dioxide of ≥ 0.02mg/l, which is the key to ensure that the drinking water has the ability to resist bacteria continuously during the transportation process, so residues are necessary to maintain the safety of water quality.

2. incomplete reaction: in the actual disinfection process, due to the complex components in the water and variable reaction conditions, some chlorine dioxide cannot fully participate in the reaction, and will exist in the water in the form of residues.

3. influence of water quality difference: the organic content, turbidity and other factors of different water sources are different. For example, when treating water sources with high turbidity and high organic content, in order to achieve ideal disinfection effect, it is often necessary to increase the dosage of chlorine dioxide, which indirectly increases the risk of residues; However, the low pollution water source requires less dosage, and the residual risk is relatively low.

Residue types and control standards

In the disinfection process of chlorine dioxide, in addition to the incomplete reaction of chlorine dioxide that may remain, chlorite (clo‹⁻) and chlorate (ClO ₃⁻) will be generated. However, people need not worry too much, because the state has strict control standards for these by-products, and their total concentration must be limited to ≤ 0.7mg/l. As long as this standard is met, it is safe to use.

Scientific application: key points for safe use of chlorine dioxide

Precise control dosing

The amount of chlorine dioxide shall be accurately controlled according to the water quality characteristics of the water source:

Ordinary water quality: generally, the recommended concentration of chlorine dioxide in drinking water is 1-2mg/l.

High turbidity water source: as there are many impurities in the water, it is difficult to disinfect, so the dosage must be appropriately increased, and the monitoring of residue must be strengthened to avoid exceeding the standard.

Low pollution water source: in view of the better water quality, the dosage can be appropriately reduced to prevent excessive residue due to excessive dosing.

Select appropriate equipment and products

High quality generator: as the core of chlorine dioxide production, chlorine dioxide generator should select equipment with strong stability and high efficiency to ensure high purity and stable output of chlorine dioxide.

Compliant products: when purchasing chlorine dioxide, high-quality products with purity ≥ 99.9% and low impurity content must be selected, and regular brands that meet national standards (xiuba chlorine dioxide disinfectant meets the above standards) must be selected to ensure disinfection effect and water safety.

Process improvement suggestions

Pretreatment stage: pre clean the water source by sedimentation, filtration and other methods to reduce the content of organic matter in the water, reduce the consumption of chlorine dioxide in the disinfection process and improve the disinfection efficiency.

Post treatment stage: use activated carbon adsorption and other technologies to deeply purify the residual clo‹and its by-products in water, further reduce the residual risk and improve water quality safety.

PH value adjustment: maintain the pH value of the water within the range of 6-8 to create a "suitable working environment" for chlorine dioxide, which can not only improve the disinfection effect, but also effectively reduce the generation of by-products.

Scientific data supports the selection of safer products

Toxicity Comparison: according to the scientific experimental data, the LD50 of chlorine dioxide is > 292mg/kg (rat experiment), while in drinking water, its residue is usually only 0.02-0.2mg/l. There is a huge gap between the actual residue and the toxicity threshold, and the safety factor is very high.

Authoritative certification: the safety of chlorine dioxide has been recognized by the World Health Organization (who) and the U.S. Environmental Protection Agency (EPA). After a lot of research and practical verification, these institutions have confirmed that chlorine dioxide does not produce carcinogenic, teratogenic and mutagenic organic chlorides and is a reliable safe disinfectant.

Long term monitoring: in the long-term practical application, a large number of practical data also show that as long as chlorine dioxide is reasonably used within the limits of the national standard, it is safe and reliable and will not cause harm to human health.

5、 Suggestions on the development of services for municipal drinking water enterprises

Establish a sound management system: formulate standardized and refined operation procedures, clarify the quality control points of each link from water source treatment to water quality detection, so that each step of operation has rules to follow.

Strengthen personnel training: regularly organize operators to participate in skill training and safety knowledge learning, improve the professional level and safety awareness of the team, and ensure standardized and accurate operation.

Introduction of intelligent monitoring system: use advanced technologies such as Internet of things and big data to build an intelligent water quality monitoring system to realize real-time monitoring and early warning of water quality data. Once abnormalities are found, measures can be taken in time.

Select high-quality partners: establish long-term and stable cooperative relations with professional and reliable equipment suppliers and testing institutions to ensure strong guarantee in equipment maintenance, technical support, water quality testing, etc.

As the core technology of modern drinking water disinfection, chlorine dioxide can achieve a perfect balance between efficient disinfection and safe residue as long as we strictly follow national standards and scientifically control each process parameter. For a large number of drinking water production practitioners, the key to ensuring drinking water safety is to establish a sound quality management system, select high-quality products and equipment, and strengthen the whole process control. Let us work together to protect the safety of every drop of water!