Degradation of ammonia nitrogen by an economic combined hydrodynamic cavitation method.

Hydrodynamic cavitation (HC) was a kind of advanced oxidation mode. There were defects in the common HC devices, such as high energy consumption, low efficiency, and easy plugging. In order to effectively utilize HC, it was urgent to research new HC devices and used them together with other traditional water treatment methods. Ozone was widely used as a water treatment agent that does not produce harmful by-products. Sodium hypochlorite (NaClO) was efficient and cheap, but too much chlorine will be harmful to water. The combination of ozone and NaClO with the HC device of propeller orifice plate can improve the dissolution and utilization rate of ozone in wastewater, reduce the use of NaClO, and avoid the generation of residual chlorine. The degradation rate reached 99.9% when the mole ratio γ of NaClO to ammonia nitrogen (NH-N) was 1.5 and the residual chlorine was near zero. As for the degradation rate of NH-N or COD of actual river water and real wastewater after biological treatment, the ideal mole ratio γ was also 1.5 and the ideal O flow rates were 1.0 L/min. The combined method has been preliminarily applied to actual water treatment and was expected to be used in more and more scenarios.