Improving the anammox performance in municipal wastewater treatment based on the powder functional carriers: A critical review

Anammox process has attracted much attention because of the significant advantages in terms of energy-saving and environment protection. While the mainstream anammox process is still difficult to be fully realized in practical engineering, it is highly feasible to achieve partial anammox in municipal wastewater treatment or improve the anammox contribution to nitrogen removal. Compared to the current widely used moving bed biofilm reactor processes, the powder functional carrier can enrich more microorganisms, promote mass transfer, circulate in the biochemical zones and reduce the energy consumption of aeration. Specific powder functional carriers may also effectively improve the anammox performance, which is a feasible solution for future upgrading of wastewater treatment plants. Therefore, this paper focuses on several powder functional carriers that have become popular and are expected to be applied in practical engineering, including biochar, iron-based material, zeolite, and diatomite. The characteristics and functions of these powder carriers were reviewed. Mechanisms of the powder carriers enhancing anammox performance were systematically summarized and analyzed in terms of the activity and abundance of functional bacteria, EPS secretion and granulation formation, electron transfer and gene expression, the quorum sensing and interaction, and nitrogen removal pathways. Moreover, this review put forward some prospects of mechanism research and engineering application of powder functional carriers enhancing anammox performance. This review provided the theoretical and technical support for improving anammox performance in municipal wastewater treatment.