Sludge age return rate

The internal circulation reflux ratio R 1=QR 1/Q, the external circulation reflux ratio R2=QR2/Q, and the total reflux ratio R=R 1+R2. In the process of pre-denitrification, nitrate nitrogen flows back to the denitrification zone through internal circulation and external circulation. As long as the returned nitrate nitrogen does not exceed the denitrification capacity in table 1, the maximum denitrification degree that can be achieved depends on the reflux ratio R. Therefore, the required minimum reflux ratio can be calculated according to the denitrification rate EDN.

EDN = NDN/(NDN+ Bei 'an)

What is the required minimum reflux ratio? r = 1/( 1-EDN)- 1

Where edn -- nitrogen removal rate NNE -- effluent nitrate nitrogen, mg/L.

Generally, in the pre-denitrification process, the reflux ratio is 2.0. If you want to further improve the nitrogen removal rate, you can continue to increase the reflux ratio. However, it must be noted that when the maximum reflux ratio is 4.0 and the reflux ratio is high, there is a danger of bringing excessive dissolved oxygen into the denitrification zone. In order to reduce the dissolved oxygen in the circulating reflux, an isolation zone can be set at the end of the aeration tank to reduce the aeration amount in this area. ?

The denitrification zone in the pre-denitrification process should be separated from the aerobic nitrification zone by a partition wall, and the denitrification zone should be equipped with a stirring device. ?

The reflux can also be adjusted according to the Nne value of the continuously monitored nitrogen removal zone.

In the process of biological nitrogen removal, the aerobic rate OVC(bo D5) of decomposing carbon compounds and the aerobic rate OVN of nitrogen oxides must be calculated separately. Then, according to the influence of saturated dissolved oxygen, the oxygen supply rate (oxygen load) OB is calculated from the sum of these two parts.