The use and maintenance of online PH meter in sewage treatment system

In order to detect the pH value of incoming water early enough to obtain timely and effective control, online PH instruments are generally installed in front of the sluice gate and have a buffer distance from the water treatment process. However, whether it is industrial sewage or domestic sewage, the water contains a lot of debris. If the sensor is directly installed in the water, the sensor glass bubble is easily broken by the debris in the water flow, causing damage to the instrument; Winding can't measure the true value of water in time. Therefore, before the sensor is installed, protect it.

Generally, a mounting and operating platform is set up at the location where the access canal has room for PH adjustment. Generally about 500m away from the gate, a hole of DN100 diameter is opened in the middle of the platform, and a stainless steel protection pipe of DN100 is taken, and the lower end is marked with 1m. Diameter of 2cm in diameter, from the open hole of the platform into the water pipe, dizzy immersed in water, according to the depth of the channel to adjust the depth of the pipe inserted, the bottom of the pipe to leave the bottom 200mm ~ 300mm, so as not to block the bottom mud The pipe, the upper end of the pipe is fixed on the platform.

After the sensor and connecting rod are installed, insert the protective tube into the protective tube. The insertion depth should be 100mm higher than the lower end of the tube so as to avoid damage to the protection tube caused by the sensor glass bulb. The sensor cable passes through the connecting rod and is connected to the converter terminal box according to the figure, which completes the installation (Figure 2). Note that when the pH electrode is installed, the protective cap on the electrode can only be removed if it is ensured that the electrode can contact the water at all times. Otherwise the electrode will dehydrate.

The daily maintenance of the on-line PH meter is known from the working principle. The electronic path between the working electrode and the reference electrode of the PH meter sensor is performed through the measured medium. The contamination of the working electrode glass film directly affects the measurement, especially in the When the sewage treatment plant is used, the cleaning work is very important. Therefore should pay attention to:

(1) Clean up the debris around the probe protection tube once a day so that the liquid touched by the probe is the measured medium.

(2) For electrodes equipped with a self-cleaning device, the probe is manually cleaned once a month. When cleaning, use a soft-bristle brush to dilute the dilute hydrochloric acid or clean water to gently brush the glass electrode so that the dirt on the electrode surface is completely removed.

(3) Special attention should be paid to that if the probe is not installed immediately after cleaning the probe, the probe must be temporarily placed in water, and it must not be left empty to avoid probe failure.

(4) If the pH electrode is not dried for a long time, there is a phenomenon of dehydration failure, you can try to immerse the electrode in the pH4.0 buffer for 24h, then remove and check whether the detection function is restored. If it still does not work, you can only replace the new electrode.

(5) Regular check (usually three months).

(6) In addition to regular cleaning of the probe and regular calibration, the online instrument should be regularly compared with a pH test paper. In particular, when the color of the incoming water is observed with the naked eye, and the meter display does not change, use a test strip for comparison, or sample to the laboratory for comparison. Once the difference between the measurement result and the test result of the test strip is too large, the sensor needs to be cleaned again and verified.

(7) Storage of pH electrode: The most important point is to prevent the electrode from dehydration. Therefore, do not remove the protective cap from the factory on the electrode before applying the pH electrode. When storing, place the electrode in a cool place and avoid direct sunlight. Store in the winter to prevent freezing, so as not to freeze the electrodes.

On-line PH meter calibration (1) In the laboratory to prepare the appropriate PH standard PH4.01PH6.86 or PH9.18 two kinds of optional, according to the fluctuations in the scope of the site to select the standard fluid. If the water quality in the site is often acidic, select two standard samples of PH4.01 and PH6.86. If the water quality in the site is often alkaline, select the standard samples of PH6.86 and PH9.18.

(2) Remove the sensor from the site and clean the probe's glass electrode with clean water.

(3) Pour the two standard solutions into two ready beakers.

(4) Immerse the electrode in the first standard solution, open the meter menu, and calibrate the first point. Different brands of instruments, check menu operation method is different, according to random instructions to operate.

(5) After the first point is calibrated, rinse the electrode with clean water, place the electrode in the second standard solution, turn the meter menu, and calibrate the second point.

(6) After the two-point calibration is completed, different brands of meters will show whether the meter passes or fails in different ways.

(7) If passed, put the electrode back into the measured liquid and put the meter into operation.

(8) If the calibration of the instrument fails, repeat the above procedure to calibrate again. If it cannot pass yet, replace the electrode. The electrode life is generally about two years.