新型好氧连续流反应器对活性污泥颗粒化的研究

Study on Granulation of Activated Sludge with a Novel Aerobic Continuous Flow Reactor

文章设计了沉淀一体式低高径比反应器(UOSB)耦合二沉池的连续流系统(UOSB-ST),对反应器内污泥筛选和机械搅拌剪切对污泥颗粒化效果和效力进行了研究。结果表明,当提供的表观气体流速为0.31 cm/s的曝气(剪切)时,反应器内接种絮状污泥的污泥体积指数(SVI_(30))可由95 mL/g(第1天)下降至74.94 mL/g(第20天),污泥平均粒径由67.61μm增大到173.9μm,沉降速度达10~27 m/h,分形维数D_(2)为1.9958,D_(pf)为1.0695,污泥结构密实、表面光滑且规整,颗粒化效果显著。继续运行至第25天,丝状菌开始在颗粒污泥表面生长,导致污泥SVI_(30)迅速上升至252.87 mL/g。此时向反应器施加转速为300 r/min的机械搅拌增加水平剪切,短期内促进了污泥的聚集和沉降性的改善(第55天SVI_(30)为41.67 mL/g,污泥平均粒径为250.69μm),污泥的优势菌群为反硝化菌属和有利于EPS分泌的菌属。研究表明,连续流系统中水力选择作用(倒置漏斗隔板上部形成的初步沉淀区)对于絮状污泥的好氧颗粒化具有重要的促进作用,搅拌提供的剪切力仅可以暂时抑制好氧颗粒污泥表面丝状菌的过度增殖,降低污泥的SVI_(30)。

A bench-scale reaction-precipitation integrated reactor(UOSB)coupled with a secondary sedimentation continuous-flow apparatus(UOSB-ST),which featured small height-diameter ratio,was designed and built up.Subsequently,experiments were conducted probing into the effects of sludge screening and the shear stress of mechanical agitation on the sludge granulation.The experiments showed that when the apparent gas flow rate generated by aeration(shearing force)increased to 0.31 cm/s,and the flocculent sludge being inoculated in the reactor,the sludge volume index(SVI_(30))declined from 95 mL/g to 74.94 mL/g after 20-day operation;as a result,the mean particle size of the sludge grew up from 67.61μm to 173.9μm,the sedimentation speed increased to 10~27 m/h,the fractal dimension D_(2) was 1.9958,D_(pf) being 1.0695.Then it could be noted the sludge was of a compact structure with smooth and regular surface.So the effect of sludge granulated was remarkable.When continue to run the system to 25th day,filamentous bacteria began to grow on the surface of the granular sludge,causing the sludge SVI_(30) to rise rapidly to 252.87 mL/g.Then,applying mechanical stirring up to 300 rpm to increase horizontal shear stress,sludge aggregation and settling character could be improved in a short period of time:SVI_(30) reduced to 41.67 mL/g on 55 th day,and the average sludge particle size being 250.69μm.The dominant flora of sludge belonged to denitrifying bacteria and the bacteria that were beneficial to EPS secretion.The experiments also showed there was key action to boost aerobic granulation of flocculent sludge owing to the‘hydraulic selection’in the continuous flow system,i.e.,the sedimentation area that had been initially formed on the upper part of the inverted funnel partition;and the shear stress by stirring could only temporarily inhibit aerobic particles and excessive proliferation of filamentous bacteria on the sludge surface to reduce the SVI_(30).