絮凝条件对絮体分形结构的影响

在85kg/m³的含沙高浊水中投加阳离子高分子聚合物,借助图像分析技术与沉降技术分析探讨了不同絮凝条件下泥沙絮凝形态学参数:絮体粒径、絮体有效质量密度、絮体自由沉速、浑液面沉速与上清液余浊等的变化规律.利用表征参数“分维”定量控制不同絮凝条件(如搅拌速率、搅拌时间、高分子浓度等)对含沙高浊水絮体结构分形特性的影响.实验证明,不合适的絮凝条件将导致絮体分形构造疏松脆弱,分维值低.絮凝条件合适时(快速絮凝强度为:r₁=300r/min,t₁=10s;慢速絮凝强度:r₂=120r/min,t₂=180s;CP浓度:0.1%),絮体分形结构处于最佳状态.该状态下的絮体具有粒径较大、沉速快、有效质量密度高、粒度分布均匀,分维值最高(D₃=2.16)的特点.而且,由静沉实验测得浑液面沉速高,上清液余浊也低.泥沙絮体分形结构达最佳时的混凝性能、沉降性能与结构密实性均较理想.

Effects of Flocculation Conditions on Aggregates Fractal Structures

By adding cationic high molecular weight polymer into high turbid water with slit content containing 85kg/m³,variation regularities of the following morphologic factors which can characterize fractal structural properties of aggregates under different flocculation conditions: such as aggregates sizes,efficient mass density of aggregates,aggregates free settling rate,turbid liquid layer settling velocity,residual turbidity of supernatant,are analyzed and discussed by using image analysis and settling technologies.The characteristic parameter "fractal dimension D" can be used to quantitatively control the effects of flocculation conditions such as stirring rate,stirring time,high molecular weight polymer concentration on the fractal properties of aggregates structures of high turbid water with slit content.It is found in experiment that when flocculation conditions are improper,fractal structures of aggregates will become loose and fragile and the value of fractal dimension D is low.When the flocculation conditions are proper(rapid flocculation strength and time separately is r₁=300r/min,t₁=10s;slow flocculation strength and time separately is(r₂=120r/min,) t₂=180s;polymer concentration is 0.1%),the fractal structures of bridging-flocculated aggregates reach the optimum compactness.Under this optimum conditions,aggregates have such characters as a bigger size,a faster free settling rate,a higher efficient mass density,size distribution in turbid suspended liquor uniform and the value of fractal dimension D is the highest((D₃=2.16).) Furthermore,the results testing from the static settling experiment indicate that the settling rate of turbid liquor layer is fast and the residual turbidity of supernatant is low also.The following behaviors of silt aggregates,such as coagulation properties,settling behaviors and the properties of structural compactness are all ideal.