二沉池污泥沉降特征参数探讨及泥位动态仿真

Parameterizations of Sludge Settle Ability and Dynamic Simulation of Sludge Blanket Level for Secondary Clarifier

二沉池作为污水处理厂的主要单元其优化运行尤为重要,实际中往往缺乏对二沉池的深入认识而导致在运行中经常发生污泥沉降性能变差的情况,基于上述问题探讨了表征污泥沉降性能的经验表征参数污泥容积指数SVI的不足,提出了二沉池水力停留时间内污泥沉降比SV的概念,同时基于固体通量理论和物料守恒建立了二沉池的数学模型,采用虚拟仪器软件开发平台(Lab VIEW)对北京某污水处理厂二沉池泥位层高度和回流污泥浓度进行了动态仿真研究,结果表明:在污泥浓度较低(MLSS<4.0 g/L)时,SV_(30)和MLSS之间呈正比例关系,可采用经验SVI值来判断污水厂的污泥沉降性能,但污泥浓度升高时(MLSS>4.0 g/L)SV_(30)和MLSS之间的线性关系发生改变,采用经验SVI值衡量污泥的沉降性能会带来较大误差;所开发的仿真模型能够较好地模拟二沉池运行工况并预测未来二沉池泥位的变化趋势,同时指导操作人员动态地改变回流比值,既可以有效地降低污泥膨胀带来的污泥流失风险,又能为污水厂的优化控制提供技术支持。

As the main unit of wastewater treatment plant,the optimal operation of secondary clarifier is very important. In practice,there is often a lack of deep understanding which leads to get the poor performance of the sludge settle ability.Based on the problems,this paper discussed the problem of the empirical characterization of sludge settle ability,and put forward the concept of SV which indicated the sludge settling ratio in the hydraulic retention time of the secondary clarifier.Based on SV,solid flux theory and mass conservation,the mathematical model of the secondary clarifier was established,and the dynamic simulation of the sludge blanket level and return sludge concentration of secondary clarifier in a wastewater treatment plant in Beijing was carried out by using the Laboratory Virtual Instrument Engineering Workbench（Lab VIEW）.The results indicated that when the activated sludge had the low concentration（MLSS4.0 g/L）,SV30 and MLSS presented the approximate linear relationship,and SVI could be used to measure the settle ability of the secondary clarifier. However,the relationship between SV30 and MLSS changes with the increase of MLSS（MLSS 4.0 g/L）,the method using SVI to measure the settle ability of the secondary clarifier can＇t be accepted due to the large error. The model can predict the change tendency of the secondary clarifier in future,and also provide technical support for the optimization control of the wastewater treatment plant.