Sharing of typical on-site abnormal situation resolution cases

1. Phenomenon

For several consecutive days, there have been individual periods when the test values of total nitrogen and ammonia nitrogen are inverted (the test value of ammonia nitrogen is greater than that of total nitrogen), which is an obviously unreasonable phenomenon. However, there are no abnormalities in the test standard solutions of the equipment. The on-site operation and maintenance staff sought help from the JIDE after-sales department.

Location: A science and technology innovation industrial park in South China, China

2. Detailed description of on-site abnormal conditions:

At 16 hours on March 27th, ammonia nitrogen was 1.64 and total nitrogen was 0.65. At 17h on the 27th, ammonia nitrogen was 3.66% and total nitrogen was 2.24

During the period from 15 hours to 22 hours on the 27th, both ammonia nitrogen and total nitrogen water samples showed an increasing and decreasing trend. The ammonia nitrogen level rose from 15 to 18 hours, and the total nitrogen level increased from 16 to 18 hours. During the period of 16 to 17 hours, the ammonia nitrogen data was higher than that of the total nitrogen

3. Problem Inference and Verification

After on-site setting information investigation, it was found that there were differences in the system time Settings for total nitrogen and ammonia nitrogen. The total nitrogen time was 1.5 minutes earlier, resulting in an advanced total nitrogen injection time of 1.5 minutes.

Further analysis of the on-site situation revealed that the sample supply pipeline of the sampler was long. The sampler's sample supply was set to be pushed back for 60 seconds. On-site testing found that it took 2 minutes and 15 seconds to fully push back, resulting in a residual water sample from the previous supply pipe. When the total nitrogen sample began to be injected at 58 minutes and 30 seconds, a residual water sample was drawn up from the supply pipe by the total nitrogen sample

To verify the conjecture, the same bottle of standard sample and clear water were tested again. The same bottle of water was tested normally without any inversion, and the 1.5 standard samples were all tested normally.

4. On-site treatment plan:

JIDE after-sales engineers offer suggestions

· Adjust the sampler's sample supply reverse push time from seconds to 180 seconds (a complete reverse push takes 135 seconds, with a default of 60 seconds) to ensure that the water sample is completely reversed.

· Adjust the sample supply time of the sampler. Start the sample supply at 56 minutes (originally 58 minutes) to ensure there is sufficient time to update the water sample in the sample supply pipeline of the sampler.

· Place the ammonia nitrogen and total nitrogen equipment together, connect the water sample tubes with three-way connectors, and take samples simultaneously.

· Modify the time setting of the total nitrogen system to ensure that both total nitrogen and ammonia nitrogen are started and sampled simultaneously.

· Verify whether the equipment is functioning properly in accordance with the 355 operation standard, retest the water sample, and then retest the standard sample. It has been verified that the equipment is normal.

5. Follow-up visit

According to the above adjustments and verifications, the on-site test equipment was normal. A follow-up visit one week later found that the equipment had returned to normal and no problems had been reproduced.

6. Summary

At present, in environmental water quality monitoring stations, it is common to see incomplete reverse push of the sample supply tube of the sampler, with the previous water sample remaining in the sample supply tube. At the same time, the total nitrogen system time is set too fast, causing the total nitrogen equipment to collect the remaining water sample in the sample supply tube in advance. So when the water sample shows a tendency to increase in height, ammonia nitrogen rises first, and the phenomenon of an inversion of ammonia nitrogen and total nitrogen will occur.

This phenomenon not only leads to the inversion of ammonia nitrogen and total nitrogen test results (obvious abnormalities), but also may cause abnormal Settings of other parameters. Therefore, when setting up, it is necessary to fully consider reducing the risk of residual water samples in the sample supply pipeline.