Strategies for ammonia recovery from wastewater: a review

The circular economy requires advanced methods to recycle waste matter such as ammonia, which can be further used as a fuel and a precursor of numerous value-added chemicals. Here, we review methods for the recovery of ammonia from wastewater with emphasis on biological and physicochemical techniques, and their applications. Biological techniques involve nitrification, denitrification, and anammox processes and the use of membrane bioreactors. Physicochemical techniques comprise adsorption, membrane filtration, ion exchange, chemical precipitation, ammonia stripping, electrochemical oxidation, photocatalytic oxidation, bioelectrochemical systems, and membrane hybrid systems. We found that nitrification and anammox processes in membrane bioreactors stand out for their cost-effectiveness, reduced sludge production, and energy efficiency. The use of struvite precipitation is an efficient, environmentally friendly, and recyclable method for ammonia removal. Membrane hybrid systems are promising for ammonia recovery, nutrient concentration, and wastewater treatment, with applications in fertilizer production and water purification. Overall, nitrogen removal ranges from 28 to 100%, and nitrogen recovery ranges from 9 to 100%.