Research On Treatment Of Urea Wastewater Via Combined Process Of Air Stripping And Biological Technology

With the rapid development of agriculture and fertilizer industry, quantity of urea wastewater rapidly increased in our country. Environmental problems that brings attached more attention in the field of environmental protection even all the world.The suitable process treating urea wastewater was confirmed by comparing many ones. Pollutants were removed most efficiently and the effluent can be drained under the standard. The process is consists of physical unit and biological unit.NH₃-N in urea wastewater mostly was removed by air stripping as the physical unit and reduced the load of the biological unit. The wastewater was treated further by aerobic-anoxic-aerobic biological process as the biological unit and the content ofNH₃-N was reduced the most lowness.By the orthogonal experiments the optimum parameters of removingNH₃-N in pipe packed stripper and ball packed stripper are obtained that the value of pH, air-liquid ratio and temperature is 11.0, 3500, and 30℃respectively. The influence of the two different fillers to the removal rate is compared under the optimum conditions. The result shows that the removal rate ofNH₃-N in pipe packed stripper is 90%, higher than in ball packed stripper by about 15%. Based on the results we have carried out further study in plant plant. The optimum parameters in plant plant are obtained that the value of pH, air-liquid ratio and temperature is 10.5, 3500, and the same as wastewater respectively. The content ofNH₃-N was reduced from 243mg/L to 85mg/L by air stripping and the removal rate can reach about 65%.TheNH₃ concentration of off gas from ammonia stripper is 37.5mg/m3 and the emmission is 4.50kg/h under emission standards for odor pollutants. The results indicate that the concentration of plant boundary or habitation can meet the standard respectively.It was found that the high mass-transfer efficiency was due to drop mass transfer through mechanism analysis of the removal ofNH₃ in pipe packed stripper. The strong turbulent shear can bring high dispersion of wastewater current in the pipes and make it possible to transfer efficiently. The strong...