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

0376735 - ÚH 2013 RIV GB eng J - Journal Article
Bubáková, Petra - Pivokonský, Martin
The influence of velocity gradient on properties and filterability of suspension formed during water treatment.
Separation and Purification Technology. Roč. 92, May (2012), s. 161-167. ISSN 1383-5866. E-ISSN 1873-3794.
[European Conference on Fluid-Particle Separation (FPS 2010). Lyon, 05.10.2010-07.10.2010]
R&D Projects: GA ČR GAP105/11/0247
Institutional research plan: CEZ:AV0Z20600510
Keywords : aggregation * fractal dimension * filtration * particle size distribution * velocity gradient
Subject RIV: BK - Fluid Dynamics
Impact factor: 2.894, year: 2012

This paper deals with the influence of the global velocity gradient G (in the range of 28–307 s^-1) 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^-1). 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 ~ 60 μm and D₂ = 1.9) formed at G > 200 s^-1 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 ~ 30 s^-1 lasted only about 30 h.
Permanent Link: http://hdl.handle.net/11104/0209063