Understand the installation and maintenance of pH meters and dissolved oxygen meters
1. Installation and maintenance of pH meters
There are two installation methods for pH meters: flow type and immersion type. The sewage treatment plant generally adopts immersion installation. For example, the pH meter of the sewage treatment plant is installed in the outlet overflow tank of the oxidation ditch, where the pH value is representative and the water flow is stable, which will not cause significant impact on the pH meter. Regular maintenance helps to accurately measure instruments and extend their service life. It should be noted that the dedicated cable between the sensor and transmitter should not be damp, otherwise the high resistance and low voltage signals of the electrodes will not be able to be transmitted to the transmitter. If the electrode is not measured, a yellow protective sleeve should be placed on it, which can keep the electrode in a moist state and help extend its service life. Every month or so, the electrodes should be cleaned. First, spray the attachments with gentle water flow, then soak the electrodes in cleaning solution for a period of time, and then rinse with clean water. The sensor bracket should also be cleaned. After each cleaning, a buffer solution should be used for calibration. Currently, among domestic pH calibration solutions, pH=4 is still acceptable, while pH=7 is not accurate enough, which will affect the calibration results. So it is best to use the manufacturer's calibration solution. The manufacturer usually provides two bottles of standard solution, one with a pH value of 7, for calibrating the instrument zero point; A bottle with a pH equal to 4 is used to calibrate the signal output slope of the instrument.
2. Installation and maintenance of dissolved oxygen analyzer
Dissolved oxygen meters are generally installed in an immersive manner, and it should be noted that the original installation bracket must be selected. The installation bracket provided by the manufacturer is made of stainless steel with a plastic chain. The immersion depth of the sensor can be changed by adjusting the chain length. The guide tube on the bracket ensures that the sensor is always in a vertical position. The support part is specially designed to transmit the fluctuations of the water surface to the immersion tube, causing slight vibration of the immersion tube and creating an additional cleaning effect on the surface of the probe through the immersion tube. Some users, in order to reduce investment, make and install brackets themselves, which often leads to poor sealing between the immersion pipe and the sensor on the bracket, and sewage seeping in, causing the connection between the dedicated cable and the sensor to be soaked in sewage for a long time, which is easy to cause damage to the sensor; Some even do not make installation brackets and directly throw the sensors into the water, which will create a greater tension between the sensors and cables, making the sensors more susceptible to damage. The dissolved oxygen probe should be gently cleaned with water every week. If any damage is found to the membrane head, it should be replaced in a timely manner. If the electrolyte is contaminated, it should also be replaced in a timely manner. When wastewater contains components such as H2S, NH3, benzene, or phenols, it is harmful to the membrane head. In such situations, it is necessary to frequently replace the film head. To determine the quality of the electrodes in the probe, one only needs to look at the color. The reference electrode should be black gray, the cathode (gold electrode) should be yellow, and the counter electrode must be bright, otherwise it should be cleaned or regenerated.
