Experimental Research on High Concentration Urea Wastewater Treatment by SBR
|School||Harbin Institute of Technology|
|Keywords||high concentration urea wastewater SBR free ammonium accumulation of nitrite nitrogen|
With the continuous development of industrialization, more and more industrial wastewater is directly drained to rivers . In recent years, our country attachs more importance to the protection of environment, so the treatment of industrial wastewater attract more attention than before. In this paper a pilot scale experiment study was carried out with condensate and boiler drainage water which contain high concentration urea as the treatment water in a petrochemical plant. We use Sequencing Batch Reactor Activated Sludge Process (SBR) to treat the urea wastewater with high level concentration. Theoretical discussion of the treatment efficiency, effect of operational factors were investigated during the experiment research.Experimental results indicated that instant inflow and limited gas supply make the reaction have a strong impetus, it could even avoid the bulge of the sluge. SBR reactor had the ability to treat the urea wastewater that the concentration was below 800 mg/L by 90% in 8 hours. When urea concentration was in the range of 600～1300 mg/L, environmental temperature was in the range of 22～30℃, pH value was in the range of 8.08～9.17, dissolved oxygen was more than 2 mg/L, the average removal efficiency of urea was 62.6%. High pH value and high concentration free ammonium is good to the accumulation of nitrite nitrogen, the average accumulation efficiency has come to 95% during the experiment.Pollutant load and pH value were the main factors influencing the treatment efficiency of SBR reactor. Experimental results indicated that when urea concentration was above 800 mg/L, the removal efficiency of urea was gradually declined with the increase of the urea concentration, the removal efficiency of ammonium and the efficiency of nitrosoation were gradually rised. When ammonium concentration was in the range of 100～150 mg/L, the removal efficiency of urea, the removal efficiency of ammonium and the efficiency of nitrosoation were gradually declined with the increase of the ammonium concentration. Prolonging the time of gas supply can improve the removal efficiency of ammonium, but it could also waste energy. When the pH value was below 9, the change of pH value had little influence on the removal efficiency of urea. With the increase of the pH value, the concentration of free ammonium was rapidly increased, it affected the growth and metabolism action of bacterium and made the effect of nitration being bad. When the temperature was below 20℃, and the average temperature is 17℃, SBR reactor was gradually weak in the treatment of the high concentration urea wastewater, the average removal efficiency was only 61.2%.