Reverse osmosis membrane biofouling: causes, consequences and countermeasures

Abstract

Biofouling has been referred to as “the Achilles heel” of reverse osmosis (RO) membrane technology; the main cause being polyamide RO membranes lack of chlorine tolerance. Biofouling increases the operating cost of water treatment by increasing RO system feed pressure (i.e., energy demand) and increasing membrane cleaning frequency, which increases downtime and reduces membrane useful life. For waters with known high biofouling potential, plant designs also may require more extensive pretreatment, which increases capital and operating costs as well as the footprint of a desalination plant. It is known from the literature that the three keys to fending off biofouling in RO systems and/or recovering from biofouling once it takes root include (1) understanding site-specific processes governing biofilm formation, (2) implementing effective biofouling pretreatment ahead of RO membranes, and (3) monitoring biofouling to enable more proactive and effective RO membrane cleaning. Herein, we present four case studies of RO membrane biofouling in seawater, municipal wastewater, brackish groundwater and industrial wastewater. Next, we describe what is known about the causes and consequences of bacterial biofilm formation and growth through a process level RO membrane biofouling model. Finally, we review common biofouling control methods including pre-treatment, chemical cleaning and the most common strategies for monitoring biofouling in RO membrane systems.