Factors affecting the performance of forward osmosis treatment for oilfield produced water from surfactant-polymer flooding

Abstract

Oilfield produced water from surfactant-polymer (SP) flooding has long been regarded as a problematic type of industrial wastewater. In this study, the forward osmosis process was employed to treat SP-produced water with anionic polyacrylamide (APAM) as the draw solution. APAM was then used as a component of the agent for subsequent SP oil displacement. The individual and combined effects of crude oil concentration, surfactant concentration, APAM molecular weight (MW), and cation type on the water flux were investigated. The results showed that the amount of water flux reduction decreased with decreasing crude oil concentration; i.e., Scenario C (1.32 L/m2•h (LMH)) > Scenario B (1.12 LMH) > Scenario A (0.92 LMH). In addition, the water flux reduction was positively but not linearly related to the concentration of pollutant components; i.e., a 50% decrease of water flux occurred within the first 60 min of the forward osmosis process. Cation type and APAM MW had a large combined effect on water flux reduction, especially for divalent Ca2+. Crude oil concentration exhibited the greatest contribution to water flux reduction. The combined effect of APAM and ions, and crude oil and SDBS to water flux reduction was comparable and greatest in both Scenario G and H, with a maximum contribution of 68.1%.