Characterization of soluble microbial products in a partial nitrification sequencing batch biofilm reactor treating high ammonia nitrogen wastewater

- Partial nitrification was successfully achieved in lab-scale SBBR.
- Nitrite accumulation rate of partial nitrification SBBR was 93.77 ± 1.04%.
- Two fluorescent components of SMP were identified by using EEM-PARAFAC.
- Fluorescence variation order of SMP was obtained from 2D-COS.

In present study, the characterization of soluble microbial products (SMP) was evaluated in a partial nitrification sequencing batch biofilm reactor (SBBR). During the stable operation of SBBR, the NH4+-N removal efficiency and nitrite accumulation ratio were 96.70 ± 0.41% and 93.77 ± 1.04%, respectively. According to excitation-emission matrix (EEM), the intensities of protein-like substances were reduced under anoxic and aerobic phases, whereas humic-like substances had little change during the whole cycle. Parallel factor analysis (PARAFAC) further indentified two components and their fluorescence intensity scores were both reduced. Synchronous fluorescence spectra revealed that the fluorescence intensity of protein-like fraction decreased with reaction time. Two-dimensional correlation spectroscopy (2D-COS) further demonstrated that protein-like fraction might decrease earlier than the other fractions. The information obtained in present study is of fundamental significance for understanding the key components in SMP and their changes in partial nitrification system by using a spectral approach.