Ammonia Nitrogen Removal by Single-stage Process: A Review

Single-stage nitrogen removal from ammonium-rich streams has been studied extensively during the last decade in view of rising cost of traditional treatment methods and stringent discharge standards. This system has been developed under different names (DEMON, CANON, OLAND, SNAP and SNAD) to carry out simultaneous aerobic, anaerobic ammonium oxidizing and denitrification reactions in the same reactor. The maximal influent ammonia concentration is 431.7 ± 25.5 mg N/L, the minimal HRT is 4 hr, the maximal nitrogen loading rate is 5.44 kg N/mday and the maximal nitrogen removal rate is 2.57 kg N/mday for the process. The single-stage process has distinct advantages in terms of saving configuration, aeration and carbon sources. This paper reviews working principles, operational characteristics, efficiency of the singlestage system, key control factors of the process and its applications for nitrogen removal.