基于光学在线监测及形态学研究的絮凝体强度分析方法

以PDA在线监测混凝过程和絮凝体形态学分析为基础,建立了絮凝体强度的分析评价方法.为了计算某一特定絮凝条件下形成絮凝体的黏结力,进行混凝实验并运用图像解析法及粒子图像测速技术研究絮凝体形态学特征.实验过程中将水样引入与光散射颗粒分析仪(PDA2000)相连的透明橡胶管内,并通过准确控制橡胶管内的水流速度梯度来改变作用于絮凝体上的剪切力,这样就可以在线监测絮体的破碎情况,然后根据PDA输出的FI曲线来确定絮凝体的临界破碎条件.根据临界破碎条件下剪切力、破碎力和黏结力的等量关系,确定黏结力系数k1,进而计算出可以表征絮凝体强度的黏结力B.该方法的有效性已经被大量以硫酸铝为混凝剂的腐殖酸混凝实验所证实.

Evaluation of Floc Strength Based on Morphological Analysis and Optical Online Monitoring

Based on morphological analysis and PDA online monitoring, a method was established for the evaluation of floc strength. In order to calculate the binding force of flocs formed under a given flocculation condition, a jar test was conducted. The morphological characteristics of flocs were studied by image analysis and the particle image velocimetry technology. A shear force was exerted on the flocs by introducing the flocculated suspension through a transparent tube where the velocity gradient value of the flow could be accurately controlled. As the tube was connected with a particle dispersion analyzer (PDA), the condition of floc breakage was monitored online and the critical condition was identified by analyzing the PDA outputs (FI curves). According to the equivalent relationship among shear force, breaking force and binding force under the critical breaking condition, the binding force coefficient k₁ could thus be determined, and the binding force B which represented the floc strength was evaluated. The validity of this method was proved by a series of experiments using aluminium sulphate as the coagulant for the flocculation of humic acid.