Removal of emulsion oil from oilfield ASP wastewater by internal circulation flotation and kinetic models

The use of alkali/surfactant/polymer (ASP) in oil exploration results in wastewater from oilfields that is more difficult to treat. In this study, emulsion ASP wastewater was treated using loop-flow flotation technology. The impact of several process variables on the removal rate of oil from wastewater was analyzed, including the concentration of partially hydrolyzed polyacrylamide (HPAM) (0–228 mg/l), temperature (10–40 °C), volumetric flow rate of the flotation gas, concentration of sodium dodecyl benzene sulfonate (SDBS) (5–27 mg/l), and alkali. A collection model was used to determine the oil removal rate. Data gathered using a factorial design revealed that the reactor efficiency was highly dependent on the performance parameters and water quality, especially the alkali/surfactant/polymer (ASP) concentration in the oilfield wastewater. The removal efficiency of the emulsion oil and the rate constant initially decreases when the HPAM concentration CHPAM is below 88 mg/l and above 164 mg/l and is stable for HPAM concentrations between 88 and 164 mg/l. The removal rate of oil greatly improves with the increase in temperature. The removal rate reaches its maximum when the volumetric flow rate of the flotation gas is at 10–15 m3/(h m3). The removal rate decreases continuously with an increase in the SDBS concentration. Because the surfactant increases the stability of the oil droplets, the removal rate decreases continuously with an increase in the SDBS concentration. The oil droplets form floc when HPAM is present in the wastewater. However, the oil droplets do not coalesce and the removal rate does not change with alkali addition. Finally, empirical equations reveal the coded factors for oil droplet removal when alkali/surfactant/polymer exist simultaneously.

► Emulsion ASP wastewater was treated based on loop flow flotation and the coarse-graining technology.
► The removal efficiency of the emulsion oil decreases as the HPAM concentration increases.
► The removal rate of the reactor greatly improves with the increase in temperature.
► When the volumetric flow rate of the flotation gas is at 10–15 m3/(h m3), the efficiency is highest.
► Alkaline/surfactant/polymer can react with each other which affect the flotation.