Page 478 - Demo

482 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGYwere high, in which the average nitrite was 5.59 mg/L and the average nitrate was 2.27 mg/L. In the next stage, the inlet ammonium concentration was raised to 20 mg/L, the outlet ammonium, nitrate and nitrite concentrations remained low, in which the average ammonium concentration in this stage was 0.54 mg/L, the average nitrite concentration was 0.09 mg/L, the average nitrate concentration was 3.25 mg/L. It can be seen that in this stage, the outlet nitrite value was low, while the nitrate concentration was higher, the nitrogen treatment efficiency was relatively high. At this time, the microorganisms had adapted to the environment. Figure 6. Evolution of ammonium, nitrate and nitrite concentrations during operation When continuing to increase the input ammonium value to the values of 40, 60, 120, and 200 mg/L, in the first days of each stage when increasing input ammonium value, the output ammonium, nitrate and nitrite values are relatively high, then gradually decrease in the following days and decrease to low levels at the end of the treatment stage. The reason is that when increasing the input ammonium value to a new value, microorganisms need time to adapt to that concentration, so in