Study On Removal Of Ammonia Nitrogen In High Concentration By Ultrasound Stripping

Ammonia nitrogen is one of the water pollutants, which derives from a wealth ofsources and is difficult to be degenerated. At present, the traditional biologicaldenitrification method and physicochemical denitrification method are the maindomestic applications, but for the sewage which concentration of ammonia nitrogen ishigher than500mg·L^-1, there exists many problems in both of the two methods. Forexample, when using the biological denitrification method, amounts of free ammonianitrogen will inhibit the activity of microbial and more oxygen is needed. When usingstripping method, one of physicochemical denitrification methods, the removalefficiency of ammonia nitrogen is low.Based on the cavitation effect of ultrasound and the precious research onultrasound of removing contaminants from sewage, this paper uses low energy densityultrasound and stripping on the treatment of high concentration of ammonia nitrogen.Try to improve the economy on the basis of the best removal effect.Lots of experiments are done for comparing the ultrasound stripping method,ultrasound method and stripping method on the ammonia nitrogen removal efficiencyand the removal paths. The removal efficiency of three methods increases withincreasing time. It goes slowly after90min. The removal efficiency of ammonianitrogen goes to its highest point at180min, and the percentage is85.84%,75.61%and62.01%（according the order above）. The ultrasound stripping method saves timefor a half than stripping method when reaching the same removal rate. For theremoval path of ammonia nitrogen, high temperature pyrogenation and the strippingpath are the main paths.For the ultrasound stripping method, the removal rate of ammonia nitrogen isincreasing when the parameters, such as pH, temperature, power and time, areincreasing. The ultrasound stripping method has a good adaptability for differentinitial concentrations of ammonia nitrogen. The optimum parameters determined bythe orthogonal experiments are65℃,120min, pH12and0.02W·mL^-1of energydensity. Under this condition, the ammonia nitrogen removal efficiency is85.69%.What’s more, the main and minor factors influencing the removal efficiency aretemperature, time, pH, and energy density. Kinetics study shows that three methods are all first order process. The rateconstants increase with the order of ultrasound stripping method, ultrasound methodand stripping method. The removal quality per minute of ammonia nitrogen achievesthe maximum at15min, and the data of ultrasound stripping is3.39mg·min^-1, whichis1.12times more than ultrasound and1.43times more than stripping. In addition, theenergy consumption of ultrasound stripping is the lowest at15min, and the data is162.10kW·h·kg^-1（NH₄⁺-N）.