Nitrogen removal and microbial community in a Simultaneous Nitrification and Denitrification Moving Bed Membrane Bioreactor (SND-MBMBR)
This study aimed to evaluate the nitrogen and organic matter removal, and the main microorganisms involved in this process, in a submerged membrane bioreactor with biofilm (SMBR-BF) operated in different concentrations of dissolved oxygen (DO) and under specific conditions for simultaneous nitrification and denitrification (SND). The SMBR-BF was operated in two phases characterized by the DO concentrations whose DO average concentrations were 2,3 ± 0,2 mg O2/L e 0,9 ± 0,3 mg O2/L for the phase I and II respectively. The system operated under the average flow of 22 ± 4 e 16 ± 1 L.h-1 in the phase I and II, respectively. It got elevated efficiency in turbidity removal, about 99 ± 1%  for both phases. The average removal for COD and BDO5 was always over 95% ± 1, in any phase and conditions of the operation. The OD concentration influenced significantly the process of conversion of total nitrogen (TN), since in the Phase I, the removal was 33 ± 8 %, while the average removal in the Phase II was 74 ± 1%. There was stability in the ammoniacal nitrogen removal in both phases on similar percentages of 90 ± 2%. On the other hand, the molecular biology outcomes have demonstrated that the abundance and the dynamics of the total of bacteria, AOB, NOB and denitrifyings (Thiothrix, Comamonas, Rhodobacter, Mycobacterium, Thermomonas, Sphingobium, Sphigopyxis, Pseudoxanthomonas, Nitrospira and, Novosphingobium) was alike as in the suspended biomass as in the biolfilm on SMBR-BF system.  It may be concluded that the reduction of DO concentration influenced the nitrogen removal, without changing the efficiency of organic matter elimination and the bacterial communities, whether the system is operated in SND configuration or in DO conditions previously exposed.