Improved anammox performance with a flow switched anaerobic baffled reactor (FSABR) modified from a common anaerobic baffled reactor (CABR)

• The reactor potential was enhanced by modifying the feeding regime.
• The sludge characteristics were promoted under the modified feeding regime.
• The problems of substrate starvation and overload were resolved.
• The kinetic simulation confirmed the superiority of the FSABR over the CABR.

An anaerobic ammonium oxidation (anammox) reactor was operated with two feeding regimes. In stage 1, the reactor was operated as a common anaerobic baffled reactor (CABR) (constant flow direction), whereas in stage 2, the reactor was modified as a flow switched anaerobic baffled reactor (FSABR) with the flow direction switching every 10 days. Adjusting the feeding regime resulted in an increase in the average nitrogen loading rate (from 1.62 to 1.80 kgN m−3 d−1) and nitrogen removal efficiency (from 75.4 to 83.1%). In addition, a maximum nitrogen removal rate of 3.49 kgN m−3 d−1 was obtained in stage 2, compared with 3.00 kgN m−3 d−1 in stage 1. The sludge properties were also enhanced; from stage 1 to stage 2, the specific anammox activity increased by more than 5-fold, the settling velocity increased from 64.1 to 71.9 m h−1, and the average particle diameter increased from 0.8 to 2.3 mm. However, there was minimal variation in the heme c content. The maximum substrate removal rates in stages 1 and 2 were 4.28 and 46.38 kgN m−3 d−1 when fitted by the Stover-Kincannon model, respectively. The results indicate that the FSABR performance was significantly enhanced compared with the CABR.