Reasons why ammonia nitrogen is higher than total nitrogen in online wastewater monitoring

Theoretically, total nitrogen should be greater than ammonia nitrogen, as total nitrogen includes all forms of nitrogen, including ammonia nitrogen. It is abnormal for ammonia nitrogen to be higher than total nitrogen. It may be due to issues in the calibration of the online monitoring equipment, such as inaccurate instrument calibration, sampling errors, or the presence of interfering substances, which lead to abnormal data. It is necessary to further investigate the specific cause. .

This post was last edited by qugd on 2023-12-27 at 10:15. 1. Losses occur during the ammonia nitrogen oxidation process as part of sample preparation. 2. Insufficient oxidation dosage, inadequate oxidation capacity, or too short oxidation time. 3. Significant deviations in the wavelength used for measurement, or interference from other components in the sample that have strong ultraviolet absorption. When treating samples with alkalis, the pH level should not exceed 9, especially for samples with high ammonia nitrogen content. It is recommended to use gas-phase molecular spectroscopy for determination, but the sample also needs to be oxidized and digested.

This post was last edited by Yang Qing on 2023-12-27 at 10:52. Is it possible then that the online ammonia nitrogen testing instruments give higher readings due to positive biases caused by the interference from such high-salt industrial wastewater? This wastewater is mainly a sodium sulfate solution resulting from the synthesis of basic zinc carbonate from zinc sulfate; after precipitation and flocculation, the levels of heavy metals are brought within acceptable limits. But there are high levels of sulfate and chloride ions?

As a supplementary note: the zinc sulfate solution produced by this department is obtained by reacting zinc monoxide (such as steel plant flue ash or zinc ash collected from rotary kilns used for zinc monoxide production) with industrial sulfuric acid. After iron removal through oxidation, copper removal via zinc powder substitution, nickel removal using thiram, and manganese removal with potassium permanganate, the resulting solution is then reacted with industrial soda ash to form basic zinc carbonate. Wastewater is the liquid phase obtained from the aforementioned reaction, which is the liquid after heavy metals have been precipitated with alkalis and the mixture has been flocculated and clarified.

This post was last edited by qugd on 2023-12-28 at 10:12. A comprehensive analysis of the original water sample can be carried out, and the processes of sampling on-site and before analysis should be reviewed as well; severe systematic deviations can arise from certain specific details, and it is difficult to clarify such issues without direct on-site observation and tracking. In such cases, it’s even impossible to know why the data will suddenly become logical again one day. When I worked at the research institute, I would go to sites on business trips and on many occasions saw analysts produce illogical analysis results. When I asked them what was going on, they couldn’t explain it; I had no choice but to go with them to the site to collect samples and take them to the laboratory for analysis. Sometimes their procedures were correct, but at other times I would suddenly notice some habitual action or minor gesture on their part that was causing the data discrepancies. Previously, the arsenic content in the raw materials and refined materials used in the reprocessing facility often reversed, and it was later found that this was caused by the mixing of sampling containers, as the adsorption effect of trace amounts of arsenic is something that on-site operators simply cannot comprehend.

Thank you, you make a very good point. Sometimes details can be confusing, and it’s hard to spot those issues without being on site. I recommend that, after the online equipment has been used for operation and maintenance, water samples be taken; these samples are first analyzed using the online equipment, and then the same samples are tested in the laboratory using **standard methods for comparison. The department currently does not possess the capability for testing; it is recommended to acidify the water samples and send them to a qualified third party for testing and comparison in order to determine the cause. Currently, online equipment suppliers are monitoring the stability of full nitrogen online devices, and based on the data, the continuous measurement results for an 80 mg/L full nitrogen standard solution are satisfactory.

The standards are in accordance with HJ353–356; it is recommended to check the 24-hour drift test results for ammonia nitrogen

For ammonia nitrogen testing in water quality using online devices from this company, the Nessler method may not be suitable; however, it should work fine after distillation. Although these online devices are based on these principles, there are differences between their operation and that in a laboratory. Therefore, since the online testing is based on the salicylic acid method, it is more appropriate to use the HJ536 salicylic acid method for comparison. Of course, using different methods for testing can help identify the reasons and assess the reliability of the data generated by the online devices……