Cranfield Water Science Institute, Cranfield University, Bedfordshire, MK43 0AL, UK.
Water Sci Technol. 2012;65(4):604-10. doi: 10.2166/wst.2012.897.
This paper demonstrates the potential for recovering dissolved methane from low temperature anaerobic processes treating domestic wastewater. In the absence of methane recovery, ca. 45% of the produced methane is released as a fugitive emission which results in a net carbon footprint of -0.47 kg CO(2e) m(-3). A poly-di-methyl-siloxane (PDMS) membrane contactor was applied to support sweep gas desorption of dissolved methane using nitrogen. The dense membrane structure controlled gaseous mass transfer thus recovery was maximised at low liquid velocities. At the lowest liquid velocity, V(L), of 0.0025 m s(-1), 72% of the dissolved methane was recovered. A vacuum was also trialled as an alternative to sweep-gas operation. At vacuum pressures below 30 mbar, reasonable methane recovery was observed at an intermediate V(L) of 0.0056 m s(-1). Results from this study demonstrate that dissolved methane recovery could increase net electrical production from low temperature anaerobic processes by ca. +0.043 kWh(e) m(-3) and reduce the net carbon footprint to +0.01 kg CO(2e) m(-3). However, further experimental work to optimise the gas-side hydrodynamics is required as well as validation of the long-term impacts of biofouling on process performance.
本文展示了从处理生活污水的低温厌氧工艺中回收溶解甲烷的潜力。如果不回收甲烷，大约 45%的产生的甲烷会作为逸散排放物释放，导致净碳足迹为-0.47 kg CO(2e) m(-3)。本文采用聚二甲基硅氧烷（PDMS）膜接触器，利用氮气支持吹扫气对溶解甲烷的解吸。致密的膜结构控制着气体传质，从而在低液体流速下实现了最大的回收。在最低的液体流速 V(L)为 0.0025 m s(-1)时，72%的溶解甲烷得到了回收。本文还尝试了真空作为吹扫气操作的替代方案。在真空压力低于 30 mbar 的情况下，在中间液体流速 V(L)为 0.0056 m s(-1)时，也观察到了合理的甲烷回收。本研究的结果表明，溶解甲烷的回收可以使低温厌氧工艺的净电产量增加约+0.043 kWh(e) m(-3)，并将净碳足迹降低至+0.01 kg CO(2e) m(-3)。然而，需要进一步进行实验工作以优化气侧流体动力学，并验证生物污垢对工艺性能的长期影响。
