Magnesium Induced Algal Flocculation in a Fluidized Bed

Abstract

The effectiveness of the use of seawater and of magnesium in the removal of microalgae from oxidation pond effluents was investigated using the jar test procedure. The results indicated that the major flocculating reaction is the magnesium hydroxide precipitation at pH 11.5. The next step was to intensify the liquid-solids separation by use of a fluidized bed flocculator packed with 800 µm inert resin particles provided with an inclined multitubular settler. The total suspended solids abatement could reach 95 % with a superficial upflow velocity of 30 m/h corresponding to a residence time through the whole unit of 5 minutes only. The energy requirement quantified by the pressure drop through the bed is very low. Besides, the waste sludge extracted from the settler is easily thickened.