The Cultivation Of Aerobic Granular Sludge And Its Simultaneous Nitrification And Denitrification

For recent decades, especially in China, the main objective for wastewater biological treatment by conventional technology was only to remove organic materials containing carbon compounds and suspended solids, less attentions were paid to removal of other nutritious substances such as nitrogen, phosphorus. According to the statistics, only about 5 percent of the municipal wastewater at present in China was treated, few of which had been dealt with nitrogen and phosphorus. The entrances of overmuch nitrogen and/or phosphorus compounds to natural water bodies not only made the quality of water environment deteriorated and affected the development of fish culture, tour industry and poultry raising, but also seriously harmed human health and the survival of animal and plant.With the development of water pollution control both internationally and domestically, it had become a hotspot to do the research on how to control the water bodies eutrophication caused by nitrogen and phosphorus, and how to remove efficiently the nitrogen and phosphorus as well as how to develop a special technics used for nitrogen and phosphorus removal, which were suitable to the situation of our country, economically and effectively.Based on the latest research findings on biological nitrogen removal in both domestic and abroad, this research changed the traditional idea from solving the ambivalent relationship in simultaneous biological nitrogen removal course by simply reforming the treatment techniques to focusing on cultivation of aerobic granular sludge capable of removing simultaneously and efficiently nitrogen and organic materials in Sequencing Batch Reactor (SBR) by controlling the operation conditions such as the ratio of COD to NH/-N, dissolved oxygen (DO), alkalinity acidity, and exploring basically the formation mechanism of it as well as its' behavior of simultaneous nitrification and denitrification.The experimental results showed that aerobic granular sludge with high activity of simultaneous nitrification and denitrification could be formed in around 2 months by effectively controlling the operation cycle and purposefully cultivation in SBR with inoculation of normal activated sludge from municipal wastewater treatment plant. Aerobic granular sludge formed with averagely 0.5-1.0 mm in diameter and well settle-ability (the sedimentation rate is between 25m/s and 40 m/s) appeared in orange yellow, smooth and approximate roundness or ellipse, and the results ofparticle-dimension analysis showed that above 20 percent of granules were about 1 .0mm in diameter. The Mixed Liquid Suspended Solids (MLSS) and the Sludge Volumetric Index (SVI) of the granular sludge system were above 4.5g/L and about 32.5, respectively, which indicated a higher concentration of effective biomass than normal aerobic activated sludge process.With the ratio of carbon to nitrogen in influent 6 and the DO in the reactor less than 3mg/L, the removal rates of COD and NH3-N reached 83.6%~92.8% and 82.3%~98.5%, respectively, in the aerobic granules SBR system, and in the meantime the concentration of NO3--N, NO2--N in effluent were all under Img/L, which shown that simultaneous nitrification and denitrification (SND) rather than sequential nitrification and denitrfication (SQND) occurred in the aerobic granular sludge SBR.With the advantages in high water shear intension and volumetric loading capacity,well settling performance and unnecessary clarifier system, as well as a high efficiency in nitrogen and COD removal for the synthetic domestic wastewater, a good application perspective of the aerobic granulation system could be predicted.