Residual chlorine detection in drinking water

- Sep 08, 2020-

In order to cooperate with the water company to realize the "Drinking Water Hygiene Standard GB5749-2006" document to provide long-term and reliable water quality monitoring guarantee to ensure the safety and sanitation of citizens' drinking water, the online automatic monitoring system for drinking water is a set of online automatic analysis instruments as the core , Automatically measure the water color, turbidity, odor and taste, naked eye, PH value, the content of trace elements such as iron and manganese in the water, as well as the total number of colonies in the water, the total number of coliforms, the remaining amount of disinfectant, and the water Pollution factors such as oxygen consumption, ammonia nitrogen and total hardness of water, using various automatic control and communication networks to form a comprehensive drinking water automatic monitoring and data processing system, which can store, process and transmit various water quality online monitoring data.

1. The field instrument can accurately measure and display the turbidity, water temperature, residual chlorine and pH value of drinking water.


2. On-site instruments can be set up for regular automatic calibration or manual calibration as required.


3. Field instrument measurement data can be accurately transmitted to the water plant computer through the central control and transmission system.


4. The water plant computer can accurately receive, display and save the data uploaded by the field instruments.


5. The waterworks computer can accurately display online measurement data and historical data.


6. The water plant can retrieve historical data of different periods and dates for report statistics and graph curve analysis, and automatically generate daily, monthly, and annual reports.


7. To ensure the integrity of the data stored in the system, the system provides data maintenance functions, such as backup, import, and export.


8. The report data contains the total emission total, and can be exported to Excel format, which is convenient for using Excel to generate more complex reports.


Three, system principle

The sampling and pretreatment unit extracts the drinking water from the water plant into the monitoring room and pretreats the water sample. The on-site instrument uses its own sampling equipment to sample the pretreated water sample and convert it into a turbidity value. , PH meter, residual chlorine value, temperature value and other water quality measurement. The data measured by the on-site analyzer and pH meter are transmitted to the data acquisition and transmission system with 4-20mA current signal or RS485 Modbus for data processing, packaging and storage. Finally, it is connected to the upper computer of the Health Bureau and the water plant through the mobile GPRS network.

System composition


(1) Sampling and pretreatment system

The programmable controller is used to control the operation of the water pump to extract the drinking water from the water plant. The tap water is drawn through the filter screen to remove large impurities and then enters the sample container. The sample container is equipped with a high-speed rotating homogenizer to break and homogenize the suspended matter. The homogenized tap water is sent to the on-site analyzer for measurement.


 The main components of the sampling system are water pump, pipeline, filter and homogenizer.


(Two) pH meter

 According to our company's experience in the field of online water quality monitoring and the actual situation of pollutant discharge companies, we recommend the British Jensprima/Jeep (Shanghai) innoCon6501P+innoSens110TpH meter with excellent performance and wide application range. The measuring principle of this meter is the glass electrode method, with AgCl/Ag as the reference electrode and the glass electrode as the indicator electrode, and the pH value is calculated by measuring the potential difference. The innoCon 6501P pH meter is widely used in process control and discharge monitoring in the chemical, electroplating, food, petroleum, pharmaceutical, biological engineering, environmental protection and other industries, and has a good performance.


1. The main functions of the instrument are as follows


9. Menu operation and simple driver. 2.jpg


10. Do two-point calibration and adjust electrode compensation through the buttons on the panel.


11. Automatic temperature compensation (ATC).


12. When there is no ATC probe, the manual temperature compensation function can be used to set the calibration value and process temperature separately.


13. All relays have hysteresis adjustment, effectively reducing the occurrence of false alarms.


14. The respectively adjustable high and low point hysteresis width (dead band) protection relay will not jump too frequently near the set point.


15. The large-screen double-row liquid crystal display is easy to clearly read out a variety of prompts, alarm status, operation and misoperation information.


16. Anti-electromagnetic interference protects both input and output signals from external interference.

The basic functions of the data acquisition and transmission system are as follows


(1) It can collect 4 analog inputs in real time, and the input signal is RS485.


(2) Various collected parameters such as pH, turbidity, temperature, residual chlorine can be processed and recorded in a binary file. The storage time of recorded historical data is only limited by the size of the electronic disk. Invoke queries and serve as the basis for related processing.


(3) The communication method uses GPRS wireless transmission to complete remote data transmission.


(4) All-Chinese user interface software to complete basic enterprise information, various channel parameter settings and reception.


(5) Real-time data display and historical data query can be carried out.


(6) To ensure the integrity of the data stored in the system, the system provides data maintenance functions, such as backup, import, and export.


(7) Provide daily, monthly, and annual reports of residual chlorine, pH value, temperature, and turbidity values. The report data includes the total emission total, and can be exported to Excel format, which is convenient to use Excel to generate more format Complex reports.


(8) The basic information database of monitored points can be established, such as name, geographic location, legal representative, enterprise code, contact phone number, etc.