Quinone electron shuttle enhanced ammonium removal performance in anaerobic ammonium oxidation coupled with Fe(III) reduction

Anaerobic ammonium oxidation coupled with Fe(III) reduction (Feammox) is a newly discovered ammonium removal process, but the low ammonium removal efficiency restricts its application in practical wastewater treatment. In this study, iron compounds Fe2O3, Fe(OH)3 and Fe3O4 were added to anaerobic sequencing batch reactors (ASBR) to explore the effect of different iron sources for the Feammox reaction on ammonium removal performance. The removal efficiencies of ammonium in Fe2O3, Fe(OH)3 and Fe3O4 groups were 34.02%, 22.8% and 7.58%, respectively. Additionally, to investigate electron shuttle effect of the quinone compound anthraquinone-2,6-disulfonate (AQDS) between Fe2O3, Fe(OH)3, Fe3O4 and ammonium and whether AQDS can improve the efficiency of Feammox, batch experiments were carried out in 250 mL serum bottles. The ammonium removal efficiency of the AQDS-Fe2O3 group was 48.53%, while those of the AQDS-Fe(OH)3 and AQDS-Fe3O4 groups were 35.63% and 15.46%, respectively. This implied that AQDS enhanced the ammonium removal performance of Feammox, especially accelerating the electron shuttle rate between Fe2O3 and ammonium. X-ray diffraction showed new iron minerals appear in the system. Moreover, modified Boltzmann model was more suitable to describe the removal of NH4+-N and showed a good correlation(R2 >0.99). This study demonstrates the significant influence of AQDS on Feammox process, which provides a theoretical basis for the application of Feammox in practical sewage treatment.