Removal of ammonia nitrogen in dyeing wastewater by ultrasound stripping.

Experiments of removal of ammonia nitrogen from dyeing wastewater by ultrasound stripping were carried out. Influencing factors on the removal rate of ammonia nitrogen including pH value,temperature and ultrasonic power were investigated. Results indicated that removal rate of ammonia nitrogen reached 90.78% under the optimal conditions as ultrasonic power 100W,temperature 30℃,stripping times of 150min and no changing of pH value of dyeing wastewater. Comparison with traditional stripping process,removal rate of ammonia nitrogen increased 30% ～40% through ultrasonic stripping process. Mechanism of ammonia nitrogen removal by ultrasound stripping is that ammonia molecules in the cavitations bubbles transformed into nitrogen molecules and hydrogen molecules via pyrolysis under high temperature and high pressure in the cavitations bubbles. Mass transfer speed of ammonia increases under supercritical condition emerging from ultrasonic cavitations,and easier release from wastewater by stripping.