Abstract:
The objective of this research was to study the treatment of cutting oily-wastewater by the electro-coagulation/flotation process (ECF) in the bubble column (BCR) and the air-lift reactor (ALR) in order to reduce the problems of chemical usage and equipment set-up in coagulation process. The effects of electrode types, distance between electrodes, and number of electrode on the treatment efficiency were evaluated in batch operation. After that, the comparison of the ECF in the BCR and ALR was conducted. The results showed that the highest removal efficiency of 99% was achieved at the optimal condition, which was the usage of 2 aluminium electrodes with 2 cm in distance between plates, with the current density of 100 - 125 A/m2 in both BCR and ALR. However, the ALR provided advantages in the recirculation of Al3+ coagulant ions and less power consumption, which could result in longer lifetime of electrodes and less sludge production. The bubble hydrodynamic parameters were found to be related with the treatment efficiency and reaction rate of both reactors. Furthermore, the continuous operations for both reactors were performed at the optimal operating condition. The efficiency of 85% was obtained at the inlet flow rate lower than 15 LPH. From the residence time distribution (RTD) study, the ALR can maintain the plug flow condition more than the BCR as flow rates were increased. The efficiencies from ALR were therefore higher than the BCR at higher inlet flowrate conditions.