Harnessing buoyancy-driven instabilities for enhanced membrane desalination

美国的工业活动产生大量复杂的废水，这些废水的处理具有挑战性，因为它们具有高浓度的溶解盐。这些沃茨通常被排放到当地的地表沃茨、下水道、威尔斯和地表，在那里它们污染了资源和生态系统。该项目使用计算机模拟和实验室实验相结合的方法来开发一种称为膜蒸馏的先进水处理工艺，该工艺可以淡化和回收复杂的废水。具体来说，我们表明，重力可以用来改善膜蒸馏内的混合，并使可再生太阳能的使用，以减少能源消耗。综合教育活动包括高中生的暑期实习，本科生的研究活动，免费教科书的开发，以及学生研究座谈会的组织。膜蒸馏是一种热脱盐过程，其中水蒸发并通过多孔膜去除盐。这项工作解决了膜蒸馏的两个长期存在的技术挑战。第一个是冷却膜附近的水，这会减缓蒸发和淡水的恢复。第二种是溶解的盐在膜附近的积累，在那里它们沉淀并堵塞膜。我们通过定向膜来解决这些问题，使重力导致凉爽，富含盐分的水从膜上下沉，在废水中产生浮力混合。我们还表明，这种混合可以通过主动加热的废水通过膜对面的表面得到加强。为此，拟议的工作使用计算流体动力学和实验室规模的实验来（1）阐明浮力混合的物理学;（2）探索使用电力或可再生太阳能主动加热废水的最佳方法;（3）验证该过程对日益关注的现实世界的城市和工业废水。我们希望这项工作通过缓解水资源短缺和改善海水淡化过程的环境可持续性来广泛影响社会，并将其应用于能源-水-气候关系。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Industrial activities in the United States generate large volumes of complex wastewaters that are challenging to treat, because they have a high concentration of dissolved salts. These wastewaters are often discharged to local surface waters, sewers, wells, and land surfaces, where they contaminate resources and ecosystems. This project uses a combination of computer simulations and laboratory experiments to develop an advanced water treatment process called membrane distillation, which can desalinate and recycle complex wastewaters. Specifically, we show that gravity can be harnessed to improve mixing within membrane distillation, and enable the use of renewable solar energy to reduce energy consumption. Integrated educational activities include summer internships for high-school students, undergraduate research activities, the development of free textbooks, and the organization of student research symposia.Membrane distillation is a thermal desalination process in which water evaporates and travels through a porous membrane that removes salts. The proposed work solves two long-standing technical challenges of membrane distillation. The first is cooling of the water near the membrane, which slows evaporation and the recovery of freshwater. The second is the accumulation of dissolved salts near the membrane, where they precipitate and clog the membrane. We address these issues by orienting the membrane so that gravity causes cool, salt-rich, water to sink away from the membrane, generating buoyant mixing within the wastewater. We also show that this mixing can be strengthened by actively heating the wastewater through a surface opposite the membrane. To that end, the proposed work uses computational fluid dynamics and bench-scale experiments to (1) elucidate the physics of the buoyant mixing; (2) explore optimal methods of actively heating the wastewater using electricity or renewable solar energy; and (3) validate the process against real-world municipal and industrial wastewaters of growing concern. We expect the work to broadly impact society by mitigating water scarcity and improving the environmental sustainability of desalination processes with critical applications to the energy-water-climate nexus.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.