Batch Reverse Osmosis (RO): Desalination with minimum wastage of energy and water

来自河流和地下蓄水层的传统优质水源已不足以满足世界各地日益增长的淡水需求。人们转而使用质量较差的水源，如微咸的地下水，这些水必须经过脱盐才能饮用。脱盐通常使用反渗透（RO）膜进行，该膜允许水通过而不包括盐。然而，现有的反渗透海水淡化厂浪费了很大一部分水源水作为废弃盐水。由于传统技术的效率低下，它们还浪费了大量的能源。现有技术的第三个缺点是RO膜的寿命短，因为它们容易被微溶的盐和胶体堵塞。间歇式反渗透是一种新的海水淡化方法，与传统工艺相比，减少了水和能源的浪费，并且不易结垢。与通过稳定的连续过程工作的常规RO不同，间歇式RO通过循环的、不稳定的过程工作，该过程尚未被充分研究或理解。中试结果表明，间歇式RO实际上是可行的，并且可能实现比传统RO技术高2-3倍的能源效率。为实现上述目标，将分三个工作组进行研究。第一个工作包将采取一个微观视图的批量反渗透过程中使用亚微米颗粒跟踪反渗透膜附近的流体运动，从而提供类似大小的颗粒，如胶体二氧化硅，往往会导致污垢的行为的理解。除了强大的直接数值模拟，这些实验将导致当地运输现象的预测工具。模拟的重要输出--例如通过膜的清洁水通量、所需驱动压力和消耗的能量--将被平均用于第二个工作包中开发的粗尺度模型。该模型将预测整个系统的性能，使我们能够选择最好的几个选项中的配置的批量RO系统，其中每一个都有一定的优点和缺点。最后，在第三个工作包，我们将建立和测试首选的设计，并将其与传统的RO系统进行比较。我们将测试该系统的能源效率、淡水回收率以及地下水中常见的污染物（特别是硫酸钙和二氧化硅）污染倾向。将对RO膜进行尸检，以检查我们的预测，并全面了解RO模块内的污垢及其分布。由于这些测试将代表分批RO系统的真实的应用，因此其结果将与工业合作伙伴合作，为该技术的后续商业化提供信息和支持。

Conventional sources of good quality water from rivers and underground aquifers are no longer sufficient to meet the growing demand for fresh water across the world. People are turning instead to sources of poorer quality, such as brackish groundwater, that have to be desalinated to make them potable. Desalination is typically carried out using reverse osmosis (RO) membranes that allow water to pass while excluding salt. However, existing RO desalination plants waste a significant fraction of the source water as rejected brine. They also waste significant amounts of energy due to inefficiency of the conventional technology. A third drawback of existing technology is the short life of the RO membranes, as they readily clog with sparingly soluble salts and colloids. Batch RO is a new approach to desalination that, compared to conventional processes, reduces the wastage of water and energy and is less prone to fouling. Unlike conventional RO that works by a steady continuous process, batch RO works by means of a cyclic, unsteady process which is not yet fully studied or understood. Pilot results have shown that batch RO is practically feasible and likely to achieve energy efficiency 2-3 times better than conventional RO technology. Specific areas of improvement needed to achieve the target performance have been identified.To achieve the aims and objectives listed above, research will be undertaken in three work packages. The first work package will take a micro view of the batch RO process by using submicron particles to track motion of fluid near the RO membranes, thus providing understanding of the behaviour of similarly-sized particles such as colloidal silica, that tend to cause fouling. Alongside powerful direct numerical simulations, these experiments will result in a predictive tool for local transport phenomena. The important outputs from the simulations - such as clean water flux through the membrane, required driving pressure and consumed energy - will be averaged for use in a coarser scale model to be developed in the second work package. This model will predict the whole system performance, enabling us to choose the best among several options for the configuration of the batch RO system, each of which has certain pros and cons. Finally, in the third work package, we will build and test the preferred design and compare it against a conventional RO system. We will test the system for energy efficiency, recovered fraction of freshwater, and tendency to foul with contaminants (especially calcium sulfate and silica) which commonly occur in groundwater. Autopsies of the RO membranes will be performed to check our predictions and gain a full understanding of fouling and its distribution within the RO module. Because the tests will be representative of real applications of the batch RO system, the results will inform and support subsequent commercialisation of the technology in collaboration with industrial partners.