Abstract:
In this study, two lab-scale sequencing batch reactors each with an effective volume of 2.3 L were operated as C-AMX
(no carrier addition) and M-AMX (magnetite carrier added) for 147 days with synthetic wastewater at an NLR range of
0.19–0.47 kgN/m3
/d. The long-term effect of magnetite on the granulation and performance of anammox bacteria in
terms of nitrogen removal and other essential parameters were confirmed. In phase I (1–24 days), M-AMX took approx imately 12 days to obtain a nitrogen removal rate (NRR) above 80 % of the initial input nitrogen. Although free nitrous
acid inhibited the reactor at a high concentration at the onset of phase III, the NRR of M-AMX recovered about 3.7
times faster than that of C-AMX. In addition, it was confirmed that the M-AMX granules had a dense and compact struc ture compared to C-AMX, and the presence of the carrier promoted the development of these resilient granules. While
the measured microbial stress gradually increased in C-AMX reactor, a vice versa was observed in the M-AMX reactor as
granulation proceeded. Compared to other alternative iron-based carrier particles, the stable crystal structure of
magnetite as a carrier created a mechanism where filamentous bacteria groups were repelled from the granulation
hence the microbial stress in the M-AMX in the final phase was 61.54 % lower than that in the C-AMX. The iron
rich environment created by the magnetite addition led to Ignavibacteria,(a Feammox bacteria) increasing significantly
in the M-AMX bioreactor.
