Treatment of alkali/surfactant/polymer flooding oilfield wastewater with polytetrafluoroethylene microfiltration membrane: Performance and membrane fouling

Polytetrafluoroethylene (PTFE) membrane has been used in the treatment of actual alkali/surfactant/polymer (ASP) flooding oilfield wastewater. However, limited information is available regarding the mechanisms of membrane fouling. Here, the membrane fouling mechanisms were analyzed by studying the membrane fouling resistance, pore blocking models, interfacial energies of foulant-membrane and foulant-foulant and contribution of major foulant to membrane fouling, which was supplemented by microscopic characterizations. The results showed that the organic foulants (anionic polyacrylamide (APAM) and crude oil) appeared on the fouled membrane. The form of membrane fouling was mainly cake layer, based on the calculation of membrane fouling resistance and the fitting of classical models. Moreover, APAM, which had a higher mass transfer rate and lower energy barrier with the membrane (141.32 kT), produced a shielding effect on crude oil fouling on the hydrophobic PTFE membrane, showing that PTFE membrane has great potential in ASP wastewater treatment. Additionally, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory verified that membrane fouling at the early stage of the microfiltration process was more serious than the later stage, resulting in the TMP reaching 50 kPa in a short time. This finding could be useful for mitigating membrane fouling and optimizing cleaning methods.