Application of dissolved air flotation (DAF) in semi-aerobic leachate treatment

Dissolved air flotation (DAF) was investigated in batch experiments as a treatment for semi-aerobic landfill leachate. This research was performed in three phases and focused on removing colour, COD, and turbidity. The first phase focused on saturator efficiency. The second phase evaluated leachate treatment using DAF alone, while the third phase consisted of coagulation with alum (Al2(SO4)3) followed by DAF. Flow rate and pressure were the two main operating parameters in the first phase, and the highest saturator efficiency (73%) was at a flow rate of 6 L/min and a pressure of 400 kPa. With the same saturator operating parameters, the removal of COD (36%), colour (33%), and turbidity (32%) was fairly low in the second phase. In the third phase, a jar test indicated that pH and alum dosage were optimum at 7 g/L and 9.5 g/L, respectively. Operating parameters evaluated in the DAF system included coagulant dosage, injection time, and retention time. The best removal in the DAF system was obtained with a 4 min injection time, a 20 min retention time, and a 2.3 g/L alum dose, resulting in 70%, 79%, and 42% removal for colour, COD, and turbidity, respectively.