Application of ultra-flocculation and turbulent micro-flotation to the removal of fine contaminants from water

Considering that the capture efficiency of micro-particles of contaminants by bubbles in the process of flotation can be described by the formula E proportional to d(p)(1.45)/D-1.83, where d(p) and D are average sizes of initial particles and bubbles accordingly, then the process can be facilitated either by way of using possibly smaller bubbles (for example bubbles generated by the electrolysis of water), or by way of implementing a stage of enlargement of particles, for example on the basis of flocculation aggregation. To ensure the generation of large and dense aggregates in a short time, the flocculation is performed in a highly non-uniform hydrodynamic field, which is specified by an average velocity gradient G=3000-10 000 s(-1) (ultra-flocculation). After hydraulically largest floccules have been separated in a continuous thin-layer settler, water is saturated with micro-bubbles and then water is passed through a static mixer, where a turbulent how defined by Reynolds number Re=8000-12000 and average velocity gradient G=300-600 s(-1) is created. As a result of this treatment, small flocs of contaminants and micro-bubbles remain in the water after passing through a thin-layer settler and will form foam flakes comprising thousands of initial micro-bubbles and millions of flocculated particles. These flakes can easily be separated from water in a continuous foam separator due to their high buoyancy (turbulent micro-flotation). This method has been developed further as a technology, and a pilot plant has been designed for separation of water-oil emulsions, water purification from soluble organic compounds, radionuclides and heavy metal ions with application of ultra-disperse sorbents. (C) 1999 Elsevier Science B.V. All rights reserved.