Design of Anti-Fouling Membrane Coatings for Desalination

Abstract

Desalination of brackish water and sea water has become increasingly implemented worldwide to combat drinking water shortages. This is especially true in remote regions where access to both fresh water and the nation’s electricity grid are missing. Renewable energy-powered reverse osmosis desalination plants seek to deliver potable water by utilizing standalone energy sources such as solar or wind, to power intermittently operated water filtration. The intermittent nature of operation, however, introduces enhanced fouling of the membrane surface due to a favorable environment for foulants to collect and grow. Thus, membrane coatings have been developed to reduce fouling occurrence. Described herein are the efforts to construct a reverse osmosis system to mimic remote plants, as well as the investigation of anti-fouling membranes under intermittent operations. A lab-scale reverse osmosis (RO) system is developed to allow testing and monitoring of water treatment processes. Multiple sensors used to measure water quality and permeate flow were incorporated inline to gather data in real time. Cross-flow RO cells utilizing flat sheet membranes enable simple sample preparation and analysis. Membrane coating technology used to improve treatment performance through enhanced antifouling properties was studied. Several coating possibilities were considered for criteria such as: cost, antifouling & anti-scaling properties, and water output quality. Polydopamine is a previously studied membrane coating, although thus far research has only extended to salt rejection of NaCl. There is a lack of research surrounding various membrane coatings when subject to real water sources, which contain a variety of salts and organic material. Additionally, intermittent operation has not been investigated. In this research, the coatings are tested under these conditions to determine their efficacy in reducing and delaying onset of membrane fouling.