Preservation and reactivation of anammox biomass: A mini review

Anaerobic ammonium oxidation (anammox) is a flourishing energy-saving and economical biological nitrogen removal process. Taking into account autotrophic anammox biomass with a long doubling time are easily inhibited by environmental factors and result in the periodic fluctuation of nitrogen removal effect. Studying long-term preservation and reactivation of anammox biomass has been key issue to maintain high efficiency and stability of anammox process as well as treat a steady flow of wastewater effectively in practical engineering applications. To overcome this limitation, it is essential to analyze recovery mechanism of anammox biomass under various storage situations. In this review, the latest research progress on the protection effect of different preservation methods on most morphological and structural characteristics of anammox biomass was summarized. The roles of temperature, protective agent, intermediate products, sludge morphology and storage time on the recovery of anammox biomass activity were also reviewed. Finally, the performance recovery of anammox bacteria under different reactivation methods were discussed. This review systematically enumerated influences of various storage methods on the metabolic characteristics and microbial community of anammox biomass during the reactivation progress, providing a basis for in-depth understanding of the anammox biomass recovery process after long starvation. Future prospects are proposed for anammox-related biomass preservation and recovery.