Recovery of dissolved methane from anaerobically treated wastewater has long been a challenge, in particular at low temperatures, due to an increased solubility of the gas in the effluent at decreased temperatures. We propose a novel approach, solvent-based membrane contactor (SMC), for dissolved methane recovery from wastewater using an omniphobic (i.e., liquid repelling) microporous membrane. In this approach, an omniphobic membrane is placed between a methane-rich feed solution (e.g., anaerobic effluent) and an organic draw solvent that has an order of magnitude higher methane solubility than water. Driven by the solubility difference, methane is then extracted from the feed into the draw, while water transport is deterred due to the low water solubility of the draw solvent. We experimentally demonstrate a high methane recovery at various temperatures and flow conditions using SMC. Specifically, we employ methane-saturated deionized water as feed and dodecane as draw, and show &gt;90% recovery at three different temperatures (15, 25 and 35 <sup>o</sup>C), which simulate psychrophilic to mesophilic conditions of anaerobic treatment. We also develop a mass transfer model to investigate the impact of temperature, flow condition, and presence of other dissolved gas species (i.e., carbon dioxide) on methane recovery. Our experimental data and predicted values from the model are in excellent agreement, showing that the energy gain from the recovered methane is higher at a lower temperature, the recovery kinetics is mainly influenced by feed flow condition, and the recovery rate is nearly unaffected by presence of other gas species. We conclude that our SMC process, when combined with a low-temperature anaerobic treatment process, has great potential for harvesting of dissolved methane as a renewable energy source from anaerobic effluents even in cold climates.<br/>

Dissolved methane harvesting using omniphobic membrane contactor

2019 Fall National Meeting

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