Disinfection process analysis of water plants

Puzzle-solving class: From factory to faucet - full analysis and safety standards of water plant disinfection process

After a series of purification treatments, tap water becomes clear and translucent, but why can't it flow directly into thousands of households? The answer is that clear does not equal sterile. In order to eliminate pathogenic microorganisms in the water and ensure its continued safety during the long journey of the pipeline network, the water plant must carry out a vital process - disinfection. This article will take you to explore in depth how water plants select disinfectants, how to accurately dose and control them, and what strict national safety standards must be followed.

After a series of purification treatments, tap water becomes clear and translucent, but why can't it flow directly into thousands of households? The answer is that clear does not equal sterile. In order to eliminate pathogenic microorganisms in the water and ensure its continued safety during the long journey of the pipeline network, the water plant must carry out a vital process - disinfection. This article will take you to explore in depth how water plants select disinfectants, how to accurately dose and control them, and what strict national safety standards must be followed.

1. The "double mission" of water plant disinfection

The disinfection process has two core goals, both of which are indispensable:

• Instant inactivation to ensure factory safety: Completely kill or inactivate pathogenic microorganisms such as bacteria and viruses in the water in the clear pool or before leaving the factory to prevent the spread of water-borne diseases.
• Maintain residual effect and protect the entire pipeline network: Ensure that there is still a trace amount of disinfectant left after leaving the factory, so that it can continue to inhibit the re-growth of bacteria in the huge water pipeline network, ensuring the safety of tap water from the water plant to your faucet. This "protective umbrella" must be effective throughout the entire process.

2. “Disinfection Guards” commonly used in water plants: characteristics, advantages and disadvantages and accurate monitoring

Different water plants will choose different "safety guards" based on the quality of the water source and the scale of treatment. Understanding their characteristics, advantages and disadvantages, and equipping them with the correct "monitoring officer" - online sensors, is the key to achieving accurate disinfection.

1. Liquid chlorine/sodium hypochlorite - the classic and main "free chlorine" disinfection

• Form and dosing: Liquid chlorine is a highly toxic liquefied gas and needs to be added through a chlorinator; sodium hypochlorite is a liquid and can be added through a metering pump or prepared on-site by electrolyzing salt, which is safer.
• Advantages: mature technology, low cost, good sterilization effect, and excellent continuous disinfection ability.
• Disadvantages: Liquid chlorine has leakage safety risks; it will react with organic matter in the water to produce harmful by-products such as trihalomethanes.
• Corresponding sensor and logic: [YuanGan Technology Online Residual Chlorine Sensor]. Its core disinfection component is free residual chlorine, which must be monitored in real time using a residual chlorine sensor.

2. Chlorine dioxide - an efficient "environmental protection star"

• Form and dosing: Unstable, need to use a chlorine dioxide generator to prepare on site and add it immediately.
• Advantages: Stronger oxidative sterilization ability, almost no trihalomethane by-products, and can effectively remove odor and color in water.
• Disadvantages: Equipment investment and operation management requirements are high; its by-product chlorite needs to be controlled.
• Corresponding sensor and logic: [YuanGan Technology Online Chlorine Dioxide Sensor]. A dedicated chlorine dioxide sensor is required for independent monitoring to ensure effectiveness and control by-products.

3. Chloramine – the long-lasting “guardian” of the pipeline network

• Form and dosage: Add chlorine first, then add ammonia in proportion, and react in water to form it.
• Advantages: Extremely stable chemical properties, lasting far longer than free chlorine in the pipeline network, and can more effectively inhibit the growth of pipeline biofilm.
• Disadvantages: Disinfection ability is weaker than free chlorine, so it is usually used as a secondary disinfectant.
• Corresponding sensor and logic (key difference): [YuanGan Technology Online Total Chlorine Sensor]. Its active ingredient is conjugated chloramine. If the residual chlorine sensor is used incorrectly, it will not reflect the true disinfection level. A total chlorine sensor must be used for monitoring.

4. Ozone - a powerful "assault vanguard"

• Form and dosing: Gas needs to be prepared on-site with an ozone generator and added through a special contact tank.
• Advantages: The strongest oxidative disinfection ability, it can instantly kill most microorganisms and effectively degrade organic pollutants.
• Disadvantages: The equipment is expensive and energy consumption is high; it is extremely unstable in water and does not have the ability to continuously disinfect, so it needs to be used in conjunction with chlorine-based disinfectants.
• Corresponding sensor and logic: [YuanGan Technology Online Ozone Sensor]. A special ozone sensor is required to strictly control its dosage concentration and contact time to ensure instant disinfection effect.

3. “Safety Red Line” of National Standards: Factory Water and Terminal Water Requirements

In order to ensure absolute safety, the national "Hygienic Standards for Drinking Water" (GB 5749-2022) sets clear margin limits for different disinfectants. This is a reasonable range that takes into account the disinfection effect (lower limit) and sensory safety and by-product control (upper limit).

The following table clearly lists these four crucial "safety red lines":

Core interpretation of the standard:

• The “lower limit” is the safety bottom line: all “≥” requirements are the minimum guarantee of disinfection effect, especially at the end of the pipe network. A margin lower than this value means a significant increase in microbial safety risks.
• The “upper limit” is the optimization goal and safety constraint: excessive dosing not only wastes costs, but also causes sensory deterioration and increases the risk of generating harmful disinfection by-products such as trihalomethanes, haloacetic acids or chlorites. Therefore, accurately controlling the factory water margin within the standard range is a reflection of the technology and management level of the water plant.

4. Intelligent disinfection system: online monitoring is the “brain” and “eyes”

To achieve stable, economical, and compliant disinfection, an intelligent control system with online sensors as the core is indispensable.

YuanGan Technology’s series of online disinfectant sensors are the core of the system, helping water plants:

• At the clean water tank/factory water point: Real-time monitoring and ensuring that the disinfectant index is stable within the national standard range to achieve accurate, safe and energy-saving dosing.
• At key nodes of the water transmission network: Ensure that the peripheral water is always higher than the national safety bottom line, and provide a decision-making basis for optimizing the operation of the pipeline network.

Conclusion Disinfection is the “last mile” of the water treatment process and the “first line of defense” for water supply safety. Choosing the correct disinfection strategy and equipping it with online monitoring sensors with precise matching and reliable performance directly determines the drinking water safety of millions of families.

YuanGan Technology provides a full range of online disinfectant sensors, which are your reliable partners in creating intelligent and precise disinfection processes. Let us join hands and use precise sensing technology to protect the safety of every drop of water from the water plant to the faucet.

—— Chongqing YuanGan Technology Co., Ltd., the water quality safety sensing expert around you