Anoxic ammonia removal using granulated nanostructured Fe oxyhydroxides and the effect of pH, temperature and potential inhibitors on the process

• Published in: Journal of water process engineering 2020-02, Vol.33, p.101066, Article 101066
• Main Authors: Desireddy, Swathi, P.C., Sabumon, M. Maliyekkal, Shihabudheen
• Format: Article
• Language: English
• Subjects: Anoxic ammonia removal; Denitrification; Inhibition; Nanostructured Fe oxyhydroxides; Nitrification; Sequencing batch reactor
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2019.101066

[Display omitted] •Economical process due to absence of oxygen and alkalinity for ammonia oxidation.•Nanostructured and granulated Fe oxyhydroxides mediated anoxic ammonia removal.•NH4+-N and TN removals (mg/L/d) of 73.1 ± 17.4 and 68.2 ± 16.9, respectively.•Optimal NH4+-N removal were at pH of 7 and temperature of 25−30 °C.•Process inhibition at (mg/L) NH4+-N (>1000), NO2−-N (>200) and S2-(>200). Simultaneous nitrification and denitrification coupled to Fe redox cycling was achieved by activated sludge flocs sourced from a sequential batch reactor (SBR), treating domestic sewage and with less efficiency using the sludge from various environments. This novel process involves bio-catalytic oxidation of NH4+-N using nanostructured Fe oxyhydroxides under anoxic environment in a SBR. NH4+-N oxidation is associated with biogenic Fe(III) reduction and, simultaneous Fe(II) oxidation which is inturn associated with NO2−-N and/or NO3−-N reduction. The internal recycling of nanostructured Fe oxyhydroxides makes NH4+-N removal to undergo multiple cycles. The synthesized oxides were identified as FeOOH based on XPS data and have an average size of 30 nm. The NH4+-N and total nitrogen removals obtained were 73.1 ± 17.4 mg/L/d and 68.2 ± 16.9 mg/L/d, respectively. Optimum conditions for NH4+-N removal were at pH of 7 and temperature of 25−30 °C. The inhibition effects of NH4+-N, NO2−-N and S2- on anoxic NH4+-N removal and the possibility of recovery from inhibition were also studied and discussed. This process does not require oxygen and alkalinity and hence is inexpensive compared to other existing techniques.