Citation:
P. Jarvis, P. Buckingham, B. Holden, B. Jefferson, Low energy ballasted flotation, Water Research, Volume 43, Issue 14, August 2009, Pages 3427-3434
Abstract:
A novel process which involves the replacement or supplementation of bubbles in
the dissolved air flotation process with low density beads is presented. The
work comprised a series of bench-scale flotation trials treating three commonly
encountered algal species (Microcystis, Melosira and Chlorella) that were
removed in a flotation cell configured as either: conventional dissolved air
flotation (DAF); ballasted flotation using low density 70 μm glass beads with a
density of 100 kg m−3; or a hybrid process of ballasted flotation combined with
conventional DAF. Results indicated that the bead only system was capable of
achieving better residual turbidity than standard DAF at bead concentrations of
500 mg L−1. Addition of beads in combination with standard DAF reduced turbidity
further to even lower residual turbidity levels. Algae removal was improved when
glass beads were dosed, but removal was dependent on algal species. Microcystis
was removed by 97% for bead only systems and this removal did not change
significantly with the addition of air bubbles. Melosira was the next best
removed algae with bead only dosed systems giving similar removals to that
achieved by standard DAF using a 10% air recycle ratio (81 and 76% removal
respectively). Chlorella was the least well removed algae by bead only systems
(63% removal). However, removal was rapidly improved to 86% by the addition of
air bubbles using only a 2% recycle ratio. Energy estimations suggested that at
least a 50% energy reduction could be achieved using the process offering a
potential route for future development of low energy separation processes for
algae rem