It is based on the biological nitrification process, adding the biological denitrification process. Its purpose is to prevent eutrophication of water and nitrogen removal of sewage treatment process. So what happened when the total nitrogen was found to exceed the limit during this treatment? Please read on! ~

It is very common for the total nitrogen in water to exceed the standard, and the TN-8000 total nitrogen online analyzer is used to monitor the total nitrogen content in water in real time! Once the situation exceeds the standard, it can be dealt with in time. There are many reasons that cause the total nitrogen in water to exceed the standard, which can be divided into the following:

1.Related to sludge load and sludge age

Because biological denitrification is carried out under the premise of biological nitrification, and must have good nitrification, can obtain efficient and stable denitrification. Therefore, the denitrification system must adopt low load and high sludge age.

2.Internal and external reflux ratio problem

Since the external reflux of the biological denitrification system is relatively simple, the biological nitrification system is smaller, mainly because most of the nitrogen in the incoming sewage has been removed, and the NO3-N concentration in the second sedimentation tank is not high, and the denitrification leads to the small risk of sludge floating. Another aspect is that the sludge settling speed of the denitrification system is fast, and the reflux ratio can be appropriately reduced under the specified requirements to ensure the sludge concentration, so as to facilitate the extension of the residence time of sewage in the aeration tank.

3.Dissolved oxygen in anoxic zone

For denitrification, DO is as low as possible to zero, so that denitrifying bacteria can do a good job of anti-Hu, thereby improving the efficiency of nitrogen removal. However, from the actual situation of the sewage treatment plant, it is still difficult to control the DO of the hypoxic zone below 0.5mg/L, which will affect the total nitrogen index in the water.

4.BOD5/TN

Denitrifying bacteria are denitrifying nitrogen in the case of decomposition of organic matter, because of this, there must be sufficient organic matter in the sewage into the anoxic area, so as to ensure the normal work of denitrification. According to the lag of the construction of the supporting pipe network of some sewage treatment plants, the BOD5 entering the plant is lower than the design value, and nitrogen, phosphorus and other indicators are equivalent to these design values, so that the influent carbon source can not meet the requirements of denitrification on the carbon source, which will cause the total nitrogen in the water to exceed the standard.

5.pH problem

In fact, we need to know that denitrifying bacteria are not sensitive to pH changes, and in the pH range of 6 to 9, normal physiological metabolism can be carried out, but the golden pH range of biological denitrification is between 6.5 and 8.0, which you also need to understand.

6.Nitrification rate by temperature

Denitrifying bacteria are not as obvious to the change of temperature as nitrifying bacteria, but the denitrification effect will still change due to the change of temperature, the higher the temperature, the higher the denitrification rate. At 30~35, the denitrification rate can increase the upper limit. When it is lower than 15, the denitrification rate will have a significant decline, to 5, denitrification will slowly stop. Therefore, in the winter when the temperature is low, in order to ensure the effect of nitrogen removal, it is necessary to increase the SRT to increase the sludge concentration or increase the number of ponds in operation.

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