The Department of Earth and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 8499000, Israel; Geological Survey of Israel, 32 Yesha'ayahu Leibowitz, Jerusalem 9692100, Israel.
The Department of Earth and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
Water Res. 2021 Jan 1;188:116508. doi: 10.1016/j.watres.2020.116508. Epub 2020 Oct 9.
Reverse osmosis (RO) seawater desalination is a widely applied technological process to supply potable water worldwide. Recently, saline groundwater (SGW) pumped from beach wells in coastal aquifers that penetrate beneath the freshwater-seawater interface is considered as a better alternative water source to RO seawater desalination as it is naturally filtered within the sediments which reduces membrane fouling and pre-treatment costs. The SGW of many coastal aquifers is anoxic - and thus, in a low redox stage - has elevated concentrations of dissolved manganese, iron and sulfides. We studied the influence of the SGW redox stage and chemistry on the performance - permeate flux and fouling properties - of RO desalination process. SGWs from three different coastal aquifers were sampled and characterized chemically, and RO desalination experiments were performed under inert and oxidized conditions. Our results show that all three aquifers have anoxic saline groundwater and two of them have intensive anaerobic oxidation of organic matter. Two aquifers were found to be in the denitrification stage or slightly lower and the third one in the sulfate reduction stage. Our results indicate that the natural redox stage of SGWs from coastal aquifers affects the performance of RO desalination. All SGW types showed better RO performance over seawater desalination. Furthermore, air oxidation of the SGW was accompanied with pH elevation, which increased the membrane fouling. Hence, keeping the feed water unexposed to atmospheric conditions for maintaining the natural reducing stage of the SGW is crucial for low fouling potential. The observed benefits of using naturally reduced SGW in RO desalination have significant implications for reduction in overall process costs.
反渗透（RO）海水淡化是一种广泛应用的技术工艺，用于为全球提供饮用水。最近，从沿海含水层中的海滩井中抽取的咸地下水（SGW）被认为是 RO 海水淡化的更好替代水源，因为它在沉积物中自然过滤，减少了膜污染和预处理成本。许多沿海含水层的 SGW 是缺氧的——因此处于低氧化还原状态——溶解的锰、铁和硫化物浓度较高。我们研究了 SGW 的氧化还原状态和化学性质对 RO 脱盐过程性能（渗透通量和污染特性）的影响。我们对来自三个不同沿海含水层的 SGW 进行了采样和化学特性分析，并在惰性和氧化条件下进行了 RO 脱盐实验。我们的结果表明，所有三个含水层都有缺氧的咸地下水，其中两个含水层存在强烈的有机物厌氧氧化。两个含水层被发现处于反硝化阶段或略低，第三个含水层处于硫酸盐还原阶段。我们的结果表明，沿海含水层 SGW 的自然氧化还原状态会影响 RO 脱盐的性能。所有 SGW 类型的 RO 性能均优于海水淡化。此外，SGW 的空气氧化伴随着 pH 值升高，这增加了膜污染。因此，为了保持低污染潜力，保持进水不暴露于大气条件以维持 SGW 的自然还原状态至关重要。在 RO 脱盐中使用自然还原的 SGW 的观察到的益处对降低整体工艺成本具有重要意义。
