Comparison of nitrogen removal and sludge characteristics between a conventional and a simultaneous nitrification–denitrification membrane bioreactor

Sludge characteristics and nitrogen removal are investigated in this study for a conventional, aerated membrane bioreactor (C-MBR) and low oxygen, simultaneous nitrification–denitrification (SND) membrane bioreactor (SND-MBR). The SND-MBR is characterized as having a higher transmembrane pressure (TMP) and larger flocs within the activated sludge (AS). Greater and more varied concentrations of soluble chemical oxygen demand (sCOD) and transparent exopolymer substances (TEPS) were also realized. The C-MBR had a positive correlation between TMP and TEPS and between sCOD and TEPS with correlation coefficients of 0.8292 and 0.8299 respectively; no correlation was detected for the SND-MBR. The SND-MBR was able to remove 80% of the total nitrogen (TN) with 48% of influent TN being removed by SND; 31% of TN was removed by the C-MBR. Characterization of microbial populations within each MBR revealed that the C-MBR favored the development of Nitrospira and Nitrobacter while the SND-MBR favored Paracoccus and Nitrosospira species.

Research highlights
► Study impact of simultaneous nitrification–denitrification (SND) on MBR operations.
► Two lab scale MBRs operated in parallel, one with SND the other with nitrification.
► SND MBR has higher fouling indicators, greater fouling rates, larger flocs.
► SND MBR removes nitrogen but results in greater fouling for MBR.