Efficient recovery of dissolved methane from anaerobically treated wastewater is crucial to realizing sustainable wastewater treatment through renewable energy production during the treatment processes. In this study, we present a novel membrane process (solvent-based membrane contactor, SMC) for recovering dissolved methane through the normal range of domestic wastewater temperatures (15 °C - 35 °C) by utilizing an omniphobic (non-wetting) microporous membrane that traps air within its pores when submerged in liquids. Driven by solubility-gradient, dissolved methane is extracted from a methane-rich aqueous solution (feed), transported across the omniphobic membrane, and absorbed into a non-polar organic solvent (draw) that has an order of magnitude higher methane solubility than does water. We fabricated the omniphobic membrane by coating a microporous polymeric membrane with silica nanoparticles, followed by a surface fluorination with low surface energy materials. The omniphobic membrane exhibited excellent wetting resistance against both water and low-surface tension organic liquids (e.g. dodecane and ethanol). Using the omniphobic membrane and dodecane as the draw solution in the SMC process, we demonstrate nearly 90% or above recovery rates of dissolved methane from methane-saturated feed water at 15 °C, 25 °C and 35 °C, simulating anaerobic effluents produced in the psychrophilic to mesophilic temperature range, while a negligible transport of water is observed due to the low water solubility in the draw. A comparative energy analysis suggests that this novel membrane process for methane recovery can enable a net energy production, with a higher value at a lower temperature (up to 0.46 MJ per m<sup>3</sup> of methane-saturated feed at 15 °C), which outperforms other dissolved methane recovery techniques. Combined with conventional anaerobic treatment processes, our technology shows a great promise to turn the currently energy-intensive wastewater treatment process into an energy-neutral or even energy-producing process.

Recovery of dissolved methane from wastewater using omniphobic membranes: Maximizing the energy benefits towards water sustainability

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.