基于数值仿真-响应表面法的二沉池优化研究

以长沙市某污水处理厂二沉池为例,采用多相流混合物模型与k-ε湍流模型结合对辐流式二沉池内速度场和污泥浓度场进行了数值模拟.以出水口悬浮物浓度(SS)为响应目标,对影响二沉池沉淀效果的3个影响因素(进水口流速、颗粒污泥粒径、挡板的淹没深度)进行中心复合设计(central composite design,CCD),并经响应表面法分析得到影响出水SS的二次回归模型,确定了二沉池沉降的最佳条件:进水口流速为0.03m·s-1,颗粒污泥粒径为220.41μm,挡板的淹没深度为3.45m,采用数值仿真模拟实验得到出水口悬浮物浓度值为2.4mg·L-1,较优化之前的仿真结果一周平均值6.7mg·L-1相比,其处理效率提高了64.2%.采用数值仿真和响应表面法结合对二沉池工艺条件进行优化研究,可以加速寻优过程,是工艺优化的辅助工具.

Optimization of sedimentation tank using numerical simulation coupled with response surface method

With a secondary clarifier of a wastewater treatment plant in Changsha as an example,the multiphase mixture model coupled with the k-epsilon turbulence model was used to simulate the fluid velocity distribution and sludge volume fraction in the circular clarifier.Considering the concentration of suspended solids(SS) at the outlet as the response objective,a quadratic model was obtained by Central Composite Design(CCD) and response surface optimization for the three factors(the inlet velocities,the diameters of the sludge flocks and the depth of baffles).The obtained optimal conditions were inlet velocity 0.03 m · s-1,diameter of the sludge flocks 220.41 μm,and depth of baffles 3.45 m.Under the optimal conditions,SS value of the numerical simulation experiment was 2.4 mg · L-1 at the outlet.Compared with the value of 6.7 mg · L-1 of SS before optimization,the operational efficiency of clarifier was increased by 64.2%.The results show that the numerical simulation coupled with response surface methodology for the optimization sedimentation tank can accelerate the optimization process.