A novel quantitative method for evaluating floc strength under turbulent flow conditions

作者：He, Junguo; Liu, Jian^*; Yuan, Yixing; Zhang, Jie

来源：Desalination and Water Treatment, 2015, 56(7): 1975-1984.

DOI：10.1080/19443994.2014.958107

• Floc strength
• Turbulent flow
• Binding force
• Breaking force
• Fractal dimension

In this paper, we established a novel quantitative method for evaluating floc strength under turbulent flow conditions. The key factors involved were the binding and breaking forces of floc. The floc's binding force was considered to be floc strength and could be described as a function of the floc diameter (d) and fractal dimension (D-f). A coefficient of binding force (k) was also developed to express the less accessible parameters, such as densities and areas. Moreover, the breaking force was proportional to the squared average velocity gradient (G) and the fourth power of d. Jar tests were conducted to test this approach using the polyaluminum chloride as the coagulant. The physical parameters involved were monitored online. A critical G value was determined to be 98.4s(-1) based on the variation of these parameters. Accordingly, the binding and breaking forces were calculated, and the k value was obtained as 6.621x10(-3). The floc strengths with various coagulant dosages were calculated and the highest floc strength was achieved at a dosage of 22.5mg/L. This method could be used to optimize coagulation in real-world settings.

• 单位
  城市水资源与水环境国家重点实验室; 哈尔滨工业大学