UCLA

With the limited amount of freshwater resources, water scarcity has been becoming a serious problem. Thus, alternative water resources such as seawater and wastewater have been attracting water suppliers’ attention. To exploit these alternative water resources, membrane filtration that has an ability to remove ionic species plays an important role. Although high salt removal efficiency (> 99%) can be achieved when membrane (i.e., reverse osmosis membrane) is operated under a great condition, membranes have relatively low removal efficiency of neutral and small molecules. In addition, the operation and application of membrane filtration is often limited by accumulation of undesired materials on the membrane surface, so called membrane fouling. To mitigate membrane fouling, source water must be appropriately pre-treated prior to be fed into membrane filtration unit. In addition, membrane must be intermittently cleaned to remove readily formed membrane fouling in a chemical/physical way, which will increase water production cost.

Herein, we investigated electrochemical approach to enhance removal of neutrally-charged boron ions in seawater with electrically-conductive reverse osmosis membranes. By applying cathodic potentials, water electrolysis was facilitated to elevate local pH near the membrane surface, which increased the boron removal efficiency. We also studied optimization of groundwater treatment train that includes pretreatment and membrane filtration. By evaluating performance of each water treatment technologies, obtained results was coupled into a mathematical model to identify an optimum treatment train with blending ratio that can produce potable water that meets drinking water standards. Lastly, we also studied impact of alternating current on mineral scale formation on the electrically-conductive membrane that treats natural groundwater. With application of alternating current on the membrane surface, electrokinetic mixing was induced, which resulted in a mitigated scale formation.