Key parameters and selection of water quality monitoring for tap water pipeline network

Tap water plays an important role in our lives and addresses the challenges of pollution. It is necessary to emphasize the need for online equipment inspection and water quality monitoring in the processes of tap water production, secondary pressurization, and building water tanks. Among them, the detection of two key parameters, residual chlorine and turbidity, is particularly important. Refer to China's national standard for tap waterGB5749-2006The standard values for residual chlorine and turbidity in the "Sanitary Standards for Drinking Water" are as follows: residual chlorine should be0.3-0.5mg/LBetween them, the turbidity should not exceed1 NTUBelow, we will provide a detailed analysis and interpretation of these two parameters.

Firstly, there is residual chlorine. From a technical perspective, residual chlorine content serves as an indicator to determine whether the water supply system is functioning properly. It is of great significance for ensuring the biological safety of water and preventing the proliferation of bacteria, viruses, and microorganisms. At multiple stages of the production and transportation of tap water, chlorine disinfection is required to kill bacteria, viruses, and microorganisms in the water, forming a disinfection barrier in the drinking water system to ensure water quality safety.

If the residual chlorine content is too high, it may cause hygiene problems, such as unpleasant odors and tastes in water. If the residual chlorine content is too low, pathogenic microorganisms may reproduce again during water transportation. This means that the regulation of chlorine content involves two important aspects: environmental protection and biosafety.

The national standards for online monitoring of residual chlorine mainly include the following two methods:DPDMethod and electrode method.

1. DPDMethod (dichloroaniline method): Measurement of color change using spectrophotometry

-Advantages:

-High sensitivity:DPDThe method can detect very low concentrations of residual chlorine, usually reaching0.01 mg/LThe detection limit.

-Good stability:DPDThe reagent is relatively stable and not easily affected by factors such as temperature, acidity, and flow rate.

-Disadvantages:

-Reagent consumption:DPDReagents need to be replaced regularly, which increases operating costs.

2. Electrode method:

-Advantages:

-Strong real-time capability: The electrode method can monitor changes in residual chlorine concentration in real time and provide real-time data.

-Remote monitoring: The electrode method can be connected to an automatic control system to achieve remote monitoring and control.

-Disadvantages:

-Low sensitivity: The sensitivity of the electrode method is relatively low and can usually be detected0.1 mg/LThe residual chlorine concentration.

-Electrode maintenance: The electrode inevitably experiences signal drift and requires regular calibration and cleaning, making maintenance more complex.

-There are many interfering factors: temperaturephTraffic volume.

Next is turbidity.

Turbidity is an important indicator for evaluating the clarity of water, which measures the dispersion of suspended particles or colloids in water. It is closely related to the transparency and chromaticity of water quality, and directly affects the appearance quality of water. Meanwhile, high turbidity can also affect the effectiveness of disinfection measures such as ultraviolet radiation or chlorine. Therefore, turbidity is a very important parameter in water quality monitoring.

However, the measurement of turbidity faces certain challenges, mainly in accordance with national standards1Require accurate measurement1NTUBelow, high range instruments cannot meet the requirements in terms of accuracy and monitoring lower limits, and water bubbles can also affect the measurement of turbidity. Therefore, accurately measuring the turbidity of tap water requires the use of precision instruments, which are much more difficult to measure than conventional ranges such as sewage and surface water.

According to the specific requirements of the water supply working environment, we need to be equipped with online residual chlorine and turbidity detection equipment, which can provide scientific basis for real-time monitoring of both to achieve online automatic control of water quality.

The following suggestions are proposed for the measurement design of two parameters:

（1）Choose to use equipment that is suitable for wide range, low detection limit, and precision.

（2）Adopting reliable monitoring methods and following national standards can accurately monitor real water quality online.

（3）The online detection equipment should have the function of remote networking with the higher-level monitoring center, which can quickly report and handle water quality exceeding the standard in a timely manner.

（4）The durability and maintenance convenience of the equipment should be considered, and the service life and maintenance cycle of the equipment should be extended.

The online equipment inspection and water quality monitoring of tap water production, secondary pressurization, and user water tanks are crucial. This not only ensures water quality, but also improves the quality of our water supply services, which has important practical significance for water operation companies. We hope to continuously optimize our water quality monitoring equipment through exploration and research, and contribute to better ensuring the safety of drinking water for the public.