Treatment of oily wastewater by floating by dissolved air

Abstract

Dissolved air flotation (DAF) processes have been effectively tested to remove hydrocarbons and suspended matter in a wide range of wastewater, including those that originate petroleum production and refining activities. DAF systems use the coagulants normally used in gravity separators. It is considered that the organic molecules with high molecular weight (10⁴) are removed with iron or aluminum, if the pH and optimal dose are used.A dissolved air flotation treatment study for wastewater from a refinery was carried out with the objective of reducing the pollutant load of oily wastewater from the gravity separation process. The process tests were carried out on Japanese manufactured flotation equipment (DAF), where the commercial products were evaluated polychlorinated aluminum (PAC), and aluminum sulfate with a commercial flocculant (CS 610). The DAF process was evaluated with the fluids at three temperatures to know its sensitivity to this parameter, the optimum operating pressure and recirculation %. It was possible to reduce the pollutant load in the wastewater of the refinery with the applied treatment by dissolved air flotation, obtaining a removal of more than 93 % for the suspended matter, 95 % for total hydrocarbons, and 98 % for turbidity for the pair                   coagulant / flocculant selected.