The influence of velocity gradient on properties and filterability of suspension formed during water treatment

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• 作者：Petra Bubakova ; ^{bubakova@ih.cas.cz} ; Martin Pivokonsky
• 关键词：Aggregation ; Fractal dimension ; Filtration ; Particle size distribution ; Velocity gradient
• 刊名：Separation and Purification Technology
• 出版年：2012
• 出版时间：18 May, 2012
• 年：2012
• 卷：92
• 期：Complete
• 页码：161-167
• 全文大小：877 K

文摘

This paper deals with the influence of the global velocity gradient G (in the range of 28-307 s^?) on properties of suspension (size and structure) formed during water treatment. Furthermore, it describes the influence of these properties on separation using depth filtration (filtration velocities of 3 and 6 m h^?). The methods of image and fractal analysis were used to determine the aggregate size and structure, respectively. The experiments were conducted in a pilot plant (a mixing tank and a rapid gravity sand filter) with ferric sulphate used as coagulant. The experiments confirmed that with an increasing velocity gradient the aggregate size decreased; the aggregate size distribution narrowed (suspension was more homogenous); the fractal dimension D₂ increased (aggregates were more compact) and the fractal dimension D_pf diminished (aggregates were more regular). The smallest and most compact aggregates (d ?#xA0;60 ¦Ìm and D₂ = 1.9) formed at G > 200 s^? displayed the best filterability with the time of filtration up to 78 h. On the contrary, the filtration of large and porous aggregates formed at G ?#xA0;30 s^? lasted only about 30 h.