This paper aims to investigate the enhancement effect of tourmaline on anaerobic ammonium oxidation (ANAMMOX) process in two sequencing batch reactors (SBRs). SBR1 was operated in parallel with SBR2, but 2 g tourmaline was added to the reactor. The results showed that when the nitrogen loading rate (NLR) was gradually increased from 181.8 to $727.3\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ , the nitrogen removal rate (NRR) of SBR2 decreased to $99.0\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ from $576.7\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ , corresponding to an increase of specific ANAMMOX activity (SAA) from 0.65 to $3.69\mathrm{mgN}/(\mathrm{gVSS}·\mathrm{h})$ .Tourmaline could control pH value to provide a stable environment for enrichment of ANAMMOX bacteria. Tourmaline promoted the growth and metabolism of ANAMMOX bacteria and enhanced the activity of the ANAMMOX reaction but was not a benefit for the granulation of ANAMMOX sludge. At the end of the start-up period, the 16S rRNA genes of ANAMMOX bacteria in SBR1 ($8.21\pm 0.07\times {10}^9\mathrm{copies}/\mathrm{mL}$ ) were two orders of magnitude higher than that in SBR2 ($5.13\pm 0.08\times {10}^7\mathrm{copies}/\mathrm{mL}$ ). The ANAMMOX sludge of SBR1 possessed a higher extracellular polymer substances (EPS) content than the SBR2 reactor ($194–287\mathrm{mg}/\mathrm{g}$ VSS in SBR1 and $203–252\mathrm{mg}/\mathrm{g}$ VSS in SBR2). The level of heme $c$ and TTC-dehydrogenase in SBR1 were still higher than that in SBR2.

The performance of the anaerobic ammonium oxidation (ANAMMOX) process was investigated in two identical sequencing batch reactors (SBRs) [designated as SBR1 (tourmaline addition) and SBR2 (check reactor)] at nitrogen loading rates (NLRs) varying from 0.73 to $4.90\mathrm{g}\mathrm{N}/(\mathrm{L}·\mathrm{d})$ and constant hydraulic retention time of 6 h. Both of the removal efficiency of ammonia nitrogen and total nitrogen were higher in SBR1 than that in SBR2 with increased NLR. The specific ANAMMOX activity (SAA) of the ANAMMOX sludge increased from 3.23 to 12.87 and from 2.83 to $8.53\mathrm{mg}\mathrm{N}/[\mathrm{g}\mathrm{volatile}\mathrm{suspended}\mathrm{solids}(\mathrm{VSS})/\mathrm{h}]$ in the SBR1 and SBR2, respectively, which increased approximately 4.0- and 3.0-fold. As compared with SBR2, SBR1 possessed the ANAMMOX sludge with higher yield coefficient and decay constant, i.e., $0.2608\mathrm{g}\mathrm{biomass}/\mathrm{g}$ substrate and $0.011/\mathrm{d}$ , respectively. According to the modified Stover–Kincannon model, the maximal substrate removal rate ($U_{\max }$ ) and saturation rate constant ($K_b$ ) of SBR1 were suggested as $125.0\mathrm{g}\mathrm{N}/(\mathrm{L}·\mathrm{d})$ and $151.7\mathrm{g}\mathrm{N}/(\mathrm{L}·\mathrm{d})$ , respectively, which were much higher than $21.6\mathrm{g}\mathrm{N}/(\mathrm{L}·\mathrm{d})$ and $26.2\mathrm{g}\mathrm{N}/(\mathrm{L}·\mathrm{d})$ of SBR2. Results showed that SBR1 obtained the excellent and stable performance, and the modified Stover–Kincannon model could be used to describe the kinetic behavior or design ANAMMOX reactor enhanced by tourmaline.