Available for Licensing
Kenneth H Carlson
At a Glance
Researchers at Colorado State University have developed an integrated treatment process composed of chemical coagulation, filtration, and membrane distillation (MD) in sequence, which can be used to treat shale oil and gas produced water efficiently. The technology will enable a cost-effective, on-site, and off-grid waste water treatment system that improves the environmental and economical sustainability of shale oil and gas industry.
Shale oil and gas wastewater is extremely challenging to treat due to its high salinity, high organic matter content, and toxicity. The salinity of shale oil and gas wastewater (up to 360,000 ppm) exceeds the desalination limit of reverse osmosis (salinity of 70,000 ppm), rendering this energy-efficient technology inappropriate for wastewater treatment. Accordingly, energy intensive thermal technologies must be employed, increasing the cost and resulting in most of the oilfield wastewater being disposed into injection wells. Membrane Distillation (MD), however, is a promising technology particularly for shale oil and gas wastewater treatment, because of its capability of utilizing geothermal energy (which naturally occurs in shale oil and gas wastewater) or waste heat from oilfield operations, tolerance to high salinity, and modular nature.
This invention provides the opportunity for a compact, on-site treatment system. It includes an integrated treatment train that enables effective treatment of shale oil and gas wastewater, utilizing membrane distillation (MD) and was performed in tandem with simple and inexpensive pretreatment steps: precipitative softening (PS) and walnut shell filtration (WSF). Figure 1, below, examples this process.
PS removed various particulate, organic, and inorganic foulants, thereby mitigating fouling and scaling potential of the wastewater. WSF displayed exceptional efficiencies (≥95%) in eliminating volatile toxic compounds including benzene, ethylbenzene, toluene, and xylenes (BTEX) along with additional gasoline and diesel range organic compounds. With pretreatment, the water vapor flux of MD decreased by only 10% at a total water recovery of 82.5%, with boron and total BTEX concentrations in the MD distillate meeting the regulatory requirement for irrigation and typical discharge limits, respectively.
The use of pretreatment also led to robust membrane reusability within three consecutive treatment cycles, with MD water flux fully restores after physical membrane cleaning. These results highlight the necessity of pretreatment prior to MD treatment of produced water and demonstrate the potential of this treatment train to achieve a cost-effective and on-site wastewater treatment system that improves the sustainability of the shale oil and gas industry.
- Improved fouling and scaling resistance
- Reduces concentrations of particulate matter
- Removes volatile toxic compounds – reducing toxicity and environmental risks of water product
- Tolerance to high salinity
- Wastewater treatment for oil and gas industry
C. A. Robbins, et al. (2022) Mitigating membrane wetting in the treatment of unconventional oil and gas wastewater by membrane distillation: A comparison of pretreatment with omniphobic membrane. Journal of Membrane Science. https://doi.org/10.1016/j.memsci.2021.120198.
Zhang, Zuoyou, et al. (2018) Effective Treatment of Shale Oil and Gas Produced Water by Membrane Distillation Coupled with Precipitative Softening and Walnut Shell Filtration. Desalination, Elsevier.
Last updated: August 2022