Study On Pretreamment And Recovery Of Ammonia Nitrogen In Coal Nitrogen Fertilizer Plant Wasterwater

Ammonia nitrogen is a key factor of water eutrophication. With the development of industry, more and more industrial ammonia nitrogen wastewater has been discharged into rivers and lakes. The industrial wastewater with high concentration of ammonia nitrogen was characterized by complicated components and high concentration pollutants, so it is difficult to degrade. Before discharged into municipal sewage treatment systems, the concentration of ammonia nitrogen in wastewater should be preprocessed to a relatively low level in order to reduce the load of sewage treatment system. Ammonia nitrogen is widely added into the various types of fertilizers. Research on resourcing by ammonia nitrogen recycling is of great significance.This study investigated ammonia nitrogen pollution of wastewater from coal nitrogen fertilizer plant, and membrane chemical reactor and hollow fibre membrane contactors are used for nitrogen removal treatment. Membrane chemical reactor combined struvite precipitation and membrane separation. Ammonia nitrogen removal rate, turbidity of effluent and struvite recovery rate were studied by using membrane chemical reactor to treat ammonia nitrogen wastewater. Using different concentrations of sulfuric acid as the separation medium treat three kinds of concentrations of ammonia nitrogen wastewater by hollow fiber membrane contactors without adjusting p H of the wastewater. The influence on ammonia nitrogen removal rate under initial concentration of ammonia nitrogen wastewater, sulfuric acid concentration and flow direction was studied.Finally, the major conclusions are as follows:(1) The studied plant use Texaco gasifier. Gasification wastewater, conversion condensate in room temperature and torch liquid seal water have large discharge and high concentrations of COD and ammonia in coal nitrogen fertilizer plant wastewater. But conversion condensate in room temperature could be reused to coal grinding section, so the main disposal object were gasification wastewater and torch liquid seal water. The ammonia concentrations of them were 180~500 mg/L and 1500~1800 mg/L respectively.(2) Mg Cl2·6H2O and Na2HPO4·12H2O were chosen as precipitation agent and the adding ratio was n(NH4+):n(Mg2+):n(PO43-)=1:1:1. This work used membrane chemical reactor to treat ammonia nitrogen wastewater with the ammonia concentration of 192.88 mg/L. Ammonia nitrogen removal rate reached more than 90%. The effluent turbidity was 20. Compared with influent and separating pond, it decreased by 50% and 85% respectively. Constant aeration in separating pond could slow down the decrease rate of membrane flux. The recovery rate of struvite could reach 94.29%.(3) Hollow fibre membrane contactors was used to treat ammonia nitrogen wastewater(274 mg/L, 380 mg/L, 478 mg/L) with the separation medium of 0.3 mol/L, 0.4 mol/L and 0.5 mol/L sulfuric acid solution respectively. Ammonia nitrogen removal rate ranged from 34% to 50%. Ammonia removal rate will decrease with the increasing of initial concentration of ammonia or decreasing of sulfuric acid concentration. When ammonia nitrogen wastewater and sulfuric acid had the same flow direction in hollow fibre membrane, ammonia removal rate was higher than reverse.