Effects of dissolved air flotation hydraulic loading rate on water treatment performance

The performance of dissolved air flotation (DAF) followed by granular media filtration for drinking water treatment was evaluated via pilot-scale studies for two water sources. The study focussed on short flocculation times (5-8 minutes), high DAF hydraulic loading rates (17-44 m/hr (7-18 gpm/ft(2))) and rapid rate filtration (10-20 m/hr (4-8 gpm/ft(2))). Excellent treatment performance was achieved in terms of DAF clarified water turbidity, filtered water turbidity, organic matter removal and filtered water production Bubble carryover from the DAF tank was mitigated by employing either internal or external air removal strategies. Overall, the results demonstrate the effectiveness of an integrated, high rate flocculation/DAF/filtration water treatment strategy.