(562c) Flexible and Low-Energy Approach for RO Desalination

Rigorous optimization in system and process design has enabled reverse osmosis (RO) membrane technology to gain foothold in various water treatment and desalination applications. However, given that water capacity demand and water product quality requirements may change over time, it is critical that the RO membrane system can be easily adapted to the new requirements. Therefore, it is desirable to impart operational flexibility to the RO system to be able to handle temporal variability in feed water quality and satisfy new treatment targets (e.g., recovery) without having to retrofit the system. Recent studies at UCLA have suggested that flexible and low-energy RO (FLERO) operation can be achieved by employing process decomposition to overcome limited operational flexibility imposed by hydraulic components such as energy recovery devices (ERDs). In order to demonstrate the enhanced operational system flexibility (allowing a wide water recovery range of 10-95% with a single system) and the high energy efficiency of the FLERO approach, a small RO/NF system platform was developed capable of autonomous, self-adaptive operation over a wide range of feed water salinity (e.g., 500 mg/L â?? 35,000 mg/L) while maintaining energy-optimal conditions. A key feature of FLERO is the ability to switch (on demand) between various operational modes (e.g. batch, continuous, and semi-batch) depending on feed conditions (e.g., salinity and temperature) and treatment targets using a single system platform. Furthermore, the present unique FLERO system design enables continuous operation (without interruptions of permeate productivity) and without the need for the high pressure feed pump used in single or multi-stage RO systems. System performance was then analyzed via process models that were validated with both laboratory and field data for brackish water and seawater desalination, as well as for nitrate removal from impaired potable groundwater sources. Both experimental and modeling results demonstrated that the innovative FLERO system platform allows for flexible operation over a wide range of product water recovery, while maintaining high energy efficiency (i.e., low energy consumption suitable for use with renewable energy). It is shown that FLERO is particularly attractive for distributed deployment in rural or isolated communities where high water recovery is critical for various water sources of different salinity levels.