High ammonia nitrogen in the effluent
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In the operation of the integrated AO system, the ammonia nitrogen level in the effluent is higher than that in the influent. What are the main reasons for this?
This phenomenon occurs as a short-term effect or when the dissolved oxygen level is low
The denitrification performance of the A/O process is quite good, especially for removing ammonia nitrogen; the key factors are dissolved oxygen and water temperature.
The removal of ammonia nitrogen in the A/O process is achieved by nitrifying bacteria that oxidize ammonia nitrogen into nitrate nitrogen
The formula for nitrifying bacteria to oxidize ammonia nitrogen is: ammonia nitrogen + oxygen → nitrite nitrogen + hydrogen； Nitrite nitrogen + oxygen -- Nitrate nitrogen.
The nitration process requires oxygen; an excess of oxygen is needed to enhance the depth of the reaction. Therefore, to increase the removal rate of ammonia nitrogen, it is essential to ensure an adequate level of dissolved oxygen, which is generally maintained at 2–3 mg/L.
Nitrifying bacteria are autotrophic organisms that use carbon dioxide and carbonic acid as carbon sources; they do not require organic matter. Therefore, high concentrations of organic matter in water are unfavorable for the growth and reproduction of nitrifying bacteria
Nitrifying bacteria have a longer generation time, and they do not possess the same resilience as aerobic bacteria; therefore, a longer sludge age is required, with 20 days or more generally being sufficient.
Water temperature has a significant impact on nitrate-fixing bacteria; generally, the best nitration efficiency is achieved at 20–35°C. For every 5°C drop in water temperature, the nitration efficiency is reduced by half. When the water temperature falls below 10°C, nitrate-fixing bacteria essentially cease their nitration activity
What type of wastewater is being treated? It is possible that the organic nitrogen in the water was ammonified. What about the total nitrogen in the effluent?
The incoming water is domestic sewage, and the production site lacks the necessary analysis facilities.