Seawater flocculation of emulsified oil and alkaline wastewaters

Abstract Seawater flocculation at high pH was investigated for the removal of emulsified oil and suspended solids from wastewater. As little as 2% seawater by volume, in conjunction with lime or caustic for pH adjustment, was required to achieve good flocculation of the oil-water emulsion. The same amount of seawater allowed efficient removal of suspended solids from alkaline industrial wastewaters and oxidation pond effluent having pH of 10.6 and higher, without addition of an OH − source. Effective flocculation was associated with the precipitation of 2–3.5 g equiv m −3 of Mg 2+ . The minimum seawater concentration for effective flocculation, in relation to pH, was predicted successfully based on the solubility of magnesium in wastewater-seawater mixtures.