Research progress on gas stripping for highly-concentrated ammonia-nitrogen wastewater treatment

Highly-concentrated ammonia-nitrogen(NH3-N) wastewater has caused serious pollution to environment with its massive discharges and high toxicity. The gas stripping method has the advantages of high removal efficiency, simple operation, and resource recovery, which shows great significance for ammonia-rich wastewater treatment with rational application. This paper introduced the principle of ammonia stripping and discussed three main factors (pH, temperature, gas to liquid ratio) that influence the efficiency. Recent novel ammonia stripping technologies were reviewed from the perspective of improving NH3-N removal efficiency and reducing operating costs. The combination processes of ammonia stripping with physicochemical and biological treatment were also summarized and evaluated with focus on achieving the reduction of other pollutants or strengthening of the processes while removing NH3-N. Finally, future prospects were proposed based on the current problems in ammonia stripping researches. Ammonia stripping should be developed towards more efficient, digital, integrated and economical, which provided guidance for its future research and application.