Studies On The Removal Of Ammonia Nitrogen In Wastewater By Microwave Technique And Its Mechanism

In recent years, microwave technique has got quick development in wastewater treatment. However, there is no report on the removal of ammonia by microwave radiation. Presently, eutrophication is serious because of discharge of wastewater containing ammonia. So it is necessary to develop cost-effective methods for the removal of ammonia nitrogen. This thesis reviewed the studies on microwave chemistry, the generation of microwave, and the research and application of microwave technique in environment remediation and wastewater treatment. A novel process for the removal of ammonia nitrogen in wastewater by microwave radiation was developed. The focus was :â‘ the effect of factors on the removal efficiency of ammonia nitrogen in simulated wastewater by microwave radiation;â‘¡the mechanisms of the removal of NH₃-N by microwave radiation;â‘¢the application of microwave technique on the removal of NH₃-N in actual coking-plant wastewater.â‘£the design of pilot-scale reactor of microwave equipment.The results of this thesis were summarized as follows:(1) The microwave power and the radiation time enhanced the removal of NH₃-N. With the increasing of pH of the wastewater, the removal of NH₃-N was increased. In this study, the wastewater were adjusted to pH = 11 before microwave treatment. The initial concentration of NH₃-N in the wastewater had no significant effect on the removal of ammonia nitrogen. The combination of microwave technique with aeration led to an increase of the removal of NH₃-N. With the increase of the wastewater volume, the removal of NH₃-N decreased.(2) The mechanism of the microwave denitrogen process was revealed as the aeration purge plays a key role in the removal of NH₃-N in wastewater. The concentrations of nitrate and nitrite in the reactor showed no significant change in the treatment of microwave process. The thermal and non-thermal effects both existed in the system. They both had contributions to the removal of ammonia nitrogen.(3) Microwave was used in treatment of actual coking-plant wastewater, and the effect of denitrogen was significant. For example, with a wastewater of initial ammonia concentration of 331 mg/L at pH=11, NH₃-N was reduced to below 10mg/L by 3 min microwave radiation; with a wastewater of initial ammonia concentration of 1350 mg/L at pH=11, NH₃-N was reduced to 50mg/L by 5 min microwave radiation; with the initial ammonia concentration of 5000 mg/L at pH=11, NH₃-N was reduced to 350mg/L by 10 min microwave radiation. It has been found that microwave radiation was satisfied in removal of ammonia nitrogen in coking-plant wastewater. Microwave technique is a new technique for wastewater containing ammonia nitrogen.(4) Based on lab-scale study, a pilot-scale apparatus was designed and manufactured and the pilot-scale research will be done in coking-plant wastewater of Wuhan Iron and Steel Company.