The Model 499AOZ sensor is intended for the continuous determination of dissolved ozone. The primary application is ozonation basins in municipal water filter plants. Pretreating the raw water with ozone reduces the amount of filter aid chemicals needed and reduces the amount of chlorine required to disinfect the finished water. Lowered chlorine dosage means a reduced level of harmful chlorination byproducts in the finished water. Ozone is also used as a disinfectant in bottling and food processing plants.
The Model 499AOZ is a membrane-covered amperometric sensor. The sensor consists of a gas-permeable membrane stretched tightly over a gold cathode. A silver anode and an electrolyte solution complete the internal circuit. During operation, ozone diffuses from the sample through the membrane. Once inside the sensor, the ozone reacts with the electrolyte solution to form an intermediate compound. A polarizing voltage applied to the cathode completely reduces the intermediate. The reduction produces a current, which the analyzer measures. The current is directly proportional to the rate at which ozone diffuses through the membrane into the sensor, which is ultimately proportional to the concentration of ozone in the sample.
Because the rate of diffusion of ozone through the membrane depends on temperature, sensor response must be corrected for changes in membrane permeability caused by temperature. A Pt 100 RTD in the Model 499AOZ Dissolved Ozone Sensor Product Data Sheet PDS 71-499AOZ/rev.D January 2006 sensor measures the temperature, and the analyzer automatically performs the correction.