Study On The Rapid Cultivation And The Operating Stability Of Aerobic Nitrifying Granular Sludge

How to enrich the nitrifying bacteria and improve the stability is difficult andimportant for aerobic nitrifying granular sludge.Many studies show that the method ofstep-increasing nitrogen concentration can enrich the nitrifying bacteria to improve thestability of the granules. But this method takes a longer period of time, and the granulesize is smaller (1.2mm or so), therefore the removal effect of total nitrogen is notsatisfied. In addition, the influence on the performance of the system after the man-madebroken granules returned to the reactor is seldom reported. Aiming at these problems, thisstudy includes the following three parts.The first part presents the study on the rapid cultivation of aerobic nitrifyinggranular sludge. There were two new cultivating strategies namely alternately changingthe influent nitrogen loading and the influent carbon and nitrogen loading adoptedrespectively in R1and R2. The traditional method of step-increasing nitrogen loadingwas adopted in R3.The results show that the full-sense nitrifying granular sludge can becultivated successfully after70days in R1and R2, but it took147days in R3. The densergranules with higher activity of nitrifying bacteria and better denitrifying performancecan be cultivated rapidly by alternately changing the influent carbon and nitrogen loadingsimultaneously. The removal rate of ammonia nitrogen and total nitrogen are about95%and70%respectively under the stable operation conditions. Overall, the physical andbio-chemical properties and the performance of denitrification are outstanding in R2.The second part presents the study on the effect of substrate and cycle time onaerobic granular sludge system, through changing the carbon source with glucose insteadof sodium acetate and shortening the cycle time to4h. The results reveal that the growthof the steady aerobic granular system almost not affected by the changing carbon source,but the favorable effect of the cycle time of4h,when the mean granules size grew to 2.3mm from1.7mm during the50days operation. COD removal efficiency of the systemalmost not affected by the changing carbon source. Although the cycle time of4hreduced the ammonia nitrogen removal efficiency to obstruct the denitrifying process,but as the granular size gradually increased to about2.3mm, the total nitrogen removalrate improved, between60%and70%.In the third part, the man-made broken granules drew back to the reactor whichresulted in the mean granular size and MLSS were both declined. After5days stableoperation, granular size gradually recovered between2.0~2.1mm, and15days later,MLSS restored to about5000mg/L. Although it produced an adverse effect on organicremoval and nitration and denitrification effects at initial stage, but both can be restoredafter5days stable operation.