Direct ammonium oxidation to nitrogen gas (Dirammox) in Alcaligenes strain HO-1: The electrode role

It has been recently suggested that Alcaligenes use a previously unknown pathway to convert ammonium into dinitrogen gas (Dirammox) via hydroxylamine (NH2OH). This fact alone already implies a significant decrease in the aeration requirements for the process, but the process would still be dependent on external aeration. This work studied the potential use of a polarised electrode as an electron acceptor for ammonium oxidation using the recently described Alcaligenes strain HO-1 as a model heterotrophic nitrifier. Results indicated that Alcaligenes strain HO-1 requires aeration for metabolism, a requirement that cannot be replaced for a polarised electrode alone. However, concomitant elimination of succinate and ammonium was observed when operating a previously grown Alcaligenes strain HO-1 culture in the presence of a polarised electrode and without aeration. The usage of a polarised electrode together with aeration did not increase the succinate nor the nitrogen removal rates observed with aeration alone. However, current density generation was observed along a feeding batch test representing an electron share of 3% of the ammonium removed in the presence of aeration and 16% without aeration. Additional tests suggested that hydroxylamine oxidation to dinitrogen gas could have a relevant role in the electron discharge onto the anode. Therefore, the presence of a polarised electrode supported the metabolic functions of Alcaligenes strain HO-1 on the simultaneous oxidation of succinate and ammonium.

Additional Info

  • Year: 2023
  • Authors: Pous, Narcís; Bañeras, Lluis; Corvini, Philippe F.-X.; Liu, Shuang-Jiang; Puig, Sebastià
  • Reference: Environmental Science and Ecotechnology, Volume 15, Article number 100253

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