State of the art of Anammox based processes for biological nitrogen removal

Nitrogen is one of the most abundant elements. About 80 percent of the air we breathe is nitrogen. It is found in the cells of all living organisms and is a major component of proteins. Inorganic nitrogen exists in the form of free-state as a gas N2, or as reactive nitrogen in the form of nitrate NO3-, nitrite NO2-, or ammonia NH3+. Organic nitrogen is found in proteins and is continually recycled by plants and animals. Since wastewater discharges containing reactive nitrogen can be toxic to aquatic life, cause oxygen depletion and eutrophication in receiving water, and affect chlorine disinfection efficiency, reducing reactive nitrogen levels from the discharges is necessary. We use various technologies to treat wastewater which contains reactive nitrogen. Over the past few years, new technologies for nitrogen removal have been developed mainly because of the increasing costs of traditional wastewater treatment technologies. Newly discovered biochemical pathways, such as the anaerobic oxidation of ammonium (ANAMMOX), and uses for nitrogen removal technologies are under discussion. Processes and technologies such as: Partial nitrification; Single reactor systems for High Ammonium Removal Over Nitrite (SHARON); Anammox; Aerobic/anoxic deammonification; Oxygen Limited Autotrophic Nitrification- Denitrification (OLAND); Completely Autotrophic Nitrogen Removal Over Nitrite (CANON); all have a high potential for nitrogen removal. These processes are suitable for treatment of high strength ammonia wastewaters such as reject water from dewatering of digested sewage sludge and wastewater from sludge digesters. This paper summarizes different aspects and experiences of several nitrogen removal processes and also the comparison of different nitrogen removal process. The main objective is to summarize various treatment techniques used for nitrogen removal and compare their performance. A simple design example of one-step reactor or two-step reactor configurations to treat digested sludge supernatant is also reported.