High-efficiency Chemical-Free Backwash Strategy for Reverse Osmosis Membrane Antifouling

High-efficiency Chemical-Free Backwash Strategy for Reverse Osmosis Membrane Antifouling
Xuanhe Zhao, Noyce Career Development Professor, Department of Mechanical Engineering
John H. Lienhard, V, Abdul Latif Jameel Professor of Water and Food, Department of Mechanical Engineering and J-WAFS

Period of performance: 

September 2017 to August 2019

Abstract: 

Reverse osmosis (RO) technology has attracted great academic and industrial interest due to the increasing demand for cleaning water in various aspects of our life and society. However, membrane fouling, the accumulation of foulants on the RO membrane, inevitably leads to a decrease in membrane permeability and thus higher energy consumption and cost. The conventional method of cleaning fouled membranes is to add chemicals such as chloramine to the feed solution, which is costly, time- and energy-inefficient, and environmentally undesirable. In this project, we propose to develop a new chemical-free cleaning strategy with low energy consumption and cleaning cost, to achieve high-efficiency RO membrane antifouling, by applying a programmed net (osmotic-minus-hydraulic) pressure profile to the RO membrane. This high-efficiency chemical-free strategy is based on two new foulant detachment mechanisms discovered by the two PIs’ groups and desalination company IDE: i) swelling-induced foulant film detachment caused by the water absorption of the highly-saline foulant film and; ii) foulant film detachment caused by the RO membrane deformation/vibration.

The research objectives of the proposed project include: i) to study the fouling process during RO membrane operation and characterize the adhesion between fouling film and RO membrane; ii) to understand new foulant-detaching mechanisms based on foulant swelling and membrane vibration; and iii) to provide optimized cleaning pressure profiles for chemical-free RO antifouling. The significance and impact of the proposed project is two-fold: i) it will provide fundamental understanding of foulant detaching mechanisms; and ii) based on this understanding, it will result in development of a high-efficiency, chemical-free antifouling strategy for RO systems. Whereas existing studies on membrane fouling and antifouling have not incorporated a deep understanding of solid mechanics; the proposed work will create a new collaboration between experts in soft material mechanics (Zhao lab) and experts in RO membrane fouling (Lienhard lab) to develop targeted, efficient, chemical-free membrane cleaning protocols.