Free chlorine, chlorine dioxide or total chlorine (incl. chloramines) are usually measured to monitor and control the disinfection of drinking water, reuse water or pool water. Our sensors are therefore applied in waterworks, cooling towers, bottle cleaning facilities, etc., where they ensure a smooth water treatment compliant to legal limits.
Our chlorine sensors and transmitters are used in water & wastewater and in the utilities of many industries such as power or food & beverage. The sensor selection depends on the application: free chlorine sensors are mainly applied in drinking and pool water, whereas chlorine dioxide sensors are often installed in drinking water, food and process water applications. Total chlorine sensors are commonly used in wastewater treatment plants to measure the effluent water’s disinfection status.
Measurement of chlorine, total chlorine and chlorine dioxide
Sensors for chlorine dioxide measurement feature a metallic cathode, which is separated from the medium by a thin membrane. Chlorine dioxide coming from the medium diffuses through this membrane and is reduced at the gold cathode. The circuit is completed by means of the silver anode and the electrolyte. The electron reduction at the cathode is proportional to the concentration of chlorine dioxide in the medium. This process works in a wide pH and temperature range.
Measuring free available chlorine is somewhat different. Here, hypochlorous acid diffuses through the membrane and produces a reaction. The presence of hypochlorous acid in the medium depends on the pH value. This dependency is compensated by means of pH measurement in the flow assembly and balancing in the transmitter. For the measurement of total chlorine, hypochlorous acid and additionally chloramines play a role in a complex system of reactions.