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Long term effect of MnO₂ powder addition on nitrogen removal by anammox process

Qiao, Sen, Bi, Zhen, Zhou, Jiti, Cheng, Yingjun, Zhang, Jie, Bhatti, Zafar
Bioresource technology 2012 v.124 pp. 520-525
cytochrome c, enzyme activity, fertilizer rates, long term effects, nitrogen, powders, transmission electron microscopy
This study examined long-term effect of MnO₂ powder (average diameter of 4–7μm) on nitrogen removal in anammox process. Two lab-scale up-flow anammox reactors were operated for 380days, one with and one without MnO₂ powder addition. During the period when only substrate concentrations varied, the maximum nitrogen removal rate in the reactor with MnO₂ addition reached 920.9g-N/m³/d. This value was 2-folds higher than that (464.6g-N/m³/d) of the reactor without MnO₂ addition. The crude enzyme activities of the anammox biomass from the two reactors was measured as 0.531±0.019 and 0.298±0.007μmol cytochrome c reduced/mg protein/min, respectively. Transmission electron microscopy observation demonstrated more undefined particles existing inside anammox bacterial cell in the reactor with MnO₂ powder addition. Furthermore, filament-like structures inside anammoxosome were observed, which formed a net-like structure with particles as the connecting nodes. The experiment results demonstrated that MnO₂ improved nitrogen removal performance of anammox process.