Relationships between microbial community structure and the performance of MBR under different dissolved oxygen

Microbial community structure and nutrient removal performance under different dissolved oxygen were investigated using Anoxic-oxic submerged membrane bioreactor (A/O-MBR) for municipal wastewater treatment. Results showed that the COD removal was not influenced markedly by the variations in DO between 0.2 mg/L and 4.0 mg/L, and the COD removal was more than 90% during the whole experiment. However, the ammonia nitrogen removal was more sensitive than COD, and the ammonia nitrogen removal dropped from 99% to 65% when DO decreased to 0.2 mg/L. The PCR-DGGE analysis showed that the diversity of total bacterial community was abundant when A/O-MBR was run at high DO (4.0 mg/L and 2.0 mg/L), and the relationships between the total bacterial community structure and the performance of MBR was not very obvious. On the contrary, the ammonia oxidizing bacterial community composition had a more obvious shift with the variation of DO concentration, and the species of ammonia oxidizing bacteria which play major role were different under different DO conditions, which were corresponded to the removal efficiency. The ammonia oxidizing bacterial community composition were similar under the DO concentration of 2.0 mg/L and 0.5 mg/L, and the nitrogen removal was enhanced.