Enhancing integrated denitrifying anaerobic methane oxidation and Anammox processes for nitrogen and methane removal: A review

The integration of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) simultaneously converts ammonium, methane, and oxidized nitrogen species (nitrite and nitrate) to harmless N2 and CO2. This integrated and complementary process achieves the nitrogen and carbon cycles in wastewater with the potential to be applied widely at full scale to realize energy-positive wastewater treatment plants (WWTPs). In this review, we summarize the collaborative and competitive interactions of DAMO–Anammox microorganisms and systematically evaluate the challenges for the full-scale application of integrated DAMO–Anammox for wastewater treatment, including their extremely slow growth rate, low metabolic activity, and limited nitrogen and methene removal rate. We examine comprehensively the critical role of bioreactor design (attached, suspended, and granular sludge systems) for biomass retention and substrate transfer. The paper also discussed strategies involving trace elements (Cu(II) and Fe(II)), Zero Valent Iron (ZVI), and External Electrostatic Fields (EEFs) to enhance the DAMO–Anammox microbial activities. Further review is provided on the addition of Humics, quinone-compound anthraquinone-2,6-disulfonate (AQDs), Fe(III), Mn(IV) as electron acceptors through extracellular electron transfer (EET) and couple with autotrophic denitrification (AuDen) (H2S and Fe(II)) to accelerate nitrogen and methane removal. Finally, a conceptual design of innovative WWTPs based on the integrated DAMO–Anammox was proposed.