Dissolved organic fouling on nanofiltration membranes

• Author / Creator

  Lee, Kai

• The fluids produced from a thermal enhanced recovery process such as steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are pumped to the surface where bitumen and water are separated. This initial fluid is known as SAGD-PW (produced water). A potential way to effectively treat SAGD-PW is to use membrane filtration technology. Membrane filtration technology has the potential to remove the dissolved organics present in SAGD-PW. Current conventional water treatment (main components include warm lime softener and weak acid cation exchanger) of SAGD-PW cannot remove effectively the dissolved organics. This treated water with still dissolved organics has the potential to foul equipment downstream of the water treatment plant. This was the motivation to investigate using membranes to treat SAGD-PW. The focus of this study was to investigate organic fouling and performance for nanofiltration (NF) membranes used to treat SAGD-PW. NF membranes were considered over other membranes (RO, UF, MF) due to the ability to remove dissolved organics and the lower energy requirements. This study also focused on the membrane surface properties (roughness, wettability, and material composition) of the six commercially available NF membranes and its impact on membrane fouling and fluid flux. The cross flow filtration fouling experiment were all conducted at the 45oC and same hydrodynamic flowing conditions and most the majority of the experiments; the synthetic feed water was identical. Two special feed water samples were used in two separate experiments to investigate the effect of salt and emulsified oil presence in the feed water. The results showed that NF membranes were capable of removing high amount (>90%) of dissolve organics present in the feed water. Both the membrane initial surface roughness and the membrane material composition played a role in overall performance and fouling behavior. The addition of salt in the process water increased the fouling and produced lower permeate rates (32% drop in permeate rate after 20 hours of filtration) compared to the case where no addition salt was added to the process water. Similarly, when the process water contains emulsified oil, the fouling was severe and permeate rate was reduced (70% drop in permeate rate after 20 hours of filtration) compared to the case where no emulsified oil was present in the process water. The fouling experimental data generated was then used to model the effect of roughness resistance. The roughness resistance was a proposed resistance that can be used to improve the predictive fouling capabilities of the conventional filtration theory equation. The development of the resistance model and validation of the predictive capability showed that it is conceivable that the membrane surface roughness plays an important role in membrane fouling. It is recommended that future studies add more complexities to the feed water composition and eventually using real SAGD-PW samples to evaluate performance and fouling characteristics. To scale up the membrane filtration process and bring the technology closer to pilot scale testing, it is also recommended that subsequent studies should integrate spiral wound membrane elements into their lab testing facility. This increases the membrane active surface area and allows for scale up to commercial applications and conditions. To further understand the fouling mechanisms that occur between membrane and foulant, future studies could investigate the interaction forces that arise during the membrane fouling process. Future studies could also advance the concept of a roughness resistance and further validate and improve the roughness resistance (Rr) model developed in this study.

• Subjects / Keywords

  • SAGD produced water
  • Roughness resistance
  • Dissolved organics
  • membrane characterization
  • Water treatment
  • Membranes

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R39W09F43

• License

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