Achievement, performance and characteristics of microbial products in a partial nitrification sequencing batch reactor as a pretreatment for anaerobic ammonium oxidation

- Partial nitrification SBR was successfully achieved under low dissolved oxygen condition.
- PN and PS contents of EPS and SMP were reduced during the achievement of partial nitrification.
- Chemical components of EPS and SMP were assessed by 3D-EEM and synchronous fluorescence spectra.
- FA was responsible for inhibiting the activity of NOB.

This study was carried out to evaluate achievement, performance and characteristics of microbial products in a partial nitrification sequencing batch reactor as a pretreatment for anaerobic ammonium oxidation (anammox). After 100 days long-term operation, the effluent NO2−-N/NH4+N ratio of the reactor was average at 1.3 and NO3−-N concentration was low by controlling low dissolved oxygen (DO) concentration, which was considered as the ideal influent for anammox. Specific oxygen uptake rate (SOUR) implied that (SOUR)NH4 and (SOUR)NO2 of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in sludge changed from 21.73 ± 0.52 and 27.39 ± 0.50 O2/g SS/h to 36.37 ± 0.85 and 12.04 ± 0.17 O2/g SS/h, respectively. The main compositions of extracellular polymeric substances (EPS) and soluble microbial products (SMP), including proteins (PN) and polysaccharides (PS), were both reduced during the achievement of partial nitrification. Three-dimensional excitation-emission matrix (3D-EEM) and synchronous fluorescence spectra revealed that PN-like, fulvic acid-like and humic acid-like substances were identified in both EPS and SMP, and their fluorescence intensities changed significantly after partial nitrification achievement. It was found from typical cycle that free ammonia (FA) may play a significant role on inhibiting the activity of NOB. The obtained results could provide more information on the performance of partial nitrification through the characteristics of microbial products when treating high ammonium wastewater.

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