The impact of physico-chemical water treatment on a novel flotation/filtration process

• Published in: Water science and technology 1999, Vol.39 (10-11), p.211-215
• Main Authors: Scriven, R.J., Ouki, S.K., Doggart, A.S., Bauer, M.J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Counter Current Dissolved Air Flotation/Filtration (COCO DAFF™); Exact sciences and technology; Filtration; Flocculation; Flocculation contact time; Flotation; Hydraulic flocculation; mean velocity gradient; mechanical flocculation; Pollution; Retention time; Separation techniques; Velocity gradient; Velocity gradients; Wastewater treatment; Water purification; Water quality; Water treatment; Water treatment and pollution
• ISSN: 0273-1223; 1996-9732
• DOI: 10.1016/S0273-1223(99)00279-6

Recent research explored the application of mechanical flocculation ahead of a novel flotation/filtration process (Counter Current Dissolved Air Flotation/Filtration - COCO DAFF™) and compared it to the process performance seen when hydraulic flocculation was used. The energy input to the system, expressed in terms of the mean velocity gradient, G (s−1), and retention time, t, were used as a guideline for comparison between the two types of flocculation. Generally, better COCO DAFF™ performance resulted from using mechanical flocculation as against that using hydraulic flocculation. High G values (in excess of 80 s−1) were found to give best results, as opposed to values of 30–60 s−1 utilised ahead of conventional treatment. The effect of flocculation contact time on the COCO DAFF™ process was also studied. Current design practice typically utilises 20–30 minutes flocculation contact time. It was found that process performance, in terms of water quality, did not deteriorate excessively if the contact time was reduced to as little as 2 minutes, but filter run times were found to be proportional to contact time.