Promotion of nitrogen removal and microbial enrichment on anammox by exogenous substance addition: A critical review

The anaerobic ammonium oxidation (anammox) process has been acknowledged as an effective nitrogen removal technology with extensive application potential. However, the growth rates of anammox bacteria (AnAOB) are extremely low, and susceptible to a handful of operational and environmental conditions, which limits the process' extensive application. In recent years, numerous researchers have conducted studies of exogenous substance addition on the performance and microbial community of anammox, and related findings have been analyzed with a focus on the effects of their promotion on performance and microbial community. This study summed up the current reports based on various metals (Zero-valent iron, Fe 2+ , Fe 3+ , iron-based material, Mn, Ni, K, Ca), organic matter (fulvic acid, humic acid), inorganic matter (biochar, activated carbon, graphene, zeolite, inorganic carbon), reaction intermediates (hydroxylamine, hydrazine) and N-acyl-homoserine lactones influencing anammox by enhancing the functional bacteria and electronic delivery, obtaining higher biological retention and specific anammox activity (SAA). This review is intended to provide the groundwork for prospective advancement and large-scale utilization of the anammox process.