Understanding membrane fouling in produced water treatment

Produced water (PW) is the largest waste stream from the petrochemical industry (about 3 barrels of PW per barrel of oil). PW is an oil-in-water emulsion containing dispersed and dissolved hydrocarbons, surface-active compounds, solid particles and usually has a high salinity. This complex mixture has to be treated before the water can be disposed or re-used, and membrane treatment is a viable method to achieve this. Membranes, however, suffer from fouling, but the extent to which this results from the many different components in PW and/or from interactions between these many components is poorly understood. This is worrying, as understanding of the causes and mechanisms of membrane fouling, is essential to develop the membrane materials and membrane processes that would allow successful PW treatment.

The aim of this thesis is to create increased understanding regarding membrane fouling by oil-in-water emulsions. The adhesion of oil droplets in an emulsion to a model surface was studied visually in a flow cell and compared to membrane filtration experiments using the same emulsion. It was found that the interaction between the salt concentration and surfactant type of the emulsion plays an important role in membrane fouling. Understanding this interaction is key to work towards new and improved membrane applications in challenging feed streams, such as PW.