Biofouling of Polyamide Membranes: Fouling Mechanisms, Current Mitigation and Cleaning Strategies, and Future Prospects

Abstract

Reverse osmosis and nanofiltration systems are continuously challenged with biofouling of polyamide membranes that are used almost exclusively for these desalination techniques. Traditionally, pretreatment and reactive membrane cleanings are employed as biofouling control methods. This in-depth review paper discusses the mechanisms of membrane biofouling and effects on performance. Current industrial disinfection techniques are reviewed, including chlorine and other chemical and non-chemical alternatives to chlorine. Operational techniques such as reactive membrane cleaning are also covered. Based on this review, there are three suggested areas of additional research offering promising, polyamide membrane-targeted biofouling minimization that are discussed. One area is membrane modification. Modification using surface coatings with inclusion of various nanoparticles, and graphene oxide within the polymer or membrane matrix, are covered. This work is in the infancy stage and shows promise for minimizing the contributions of current membranes themselves in promoting biofouling, as well as creating oxidant-resistant membranes. Another area of suggested research is chemical disinfectants for possible application directly on the membrane. Likely disinfectants discussed herein include nitric oxide donor compounds, dichloroisocyanurate, and chlorine dioxide. Finally, proactive cleaning, which aims to control the extent of biofouling by cleaning before it negatively affects membrane performance, shows potential for low- to middle-risk systems.

Current Advances in Biofouling Mitigation in Membranes for Water Treatment: An Overview

“…[26]. On the other hand, higher ionic strength and acidic pH promote bacterial adhesion by modifying the membrane surface in terms of pore size or shape [27].…”

“…The influence of the feed flow velocity on the fouling rate is fundamental to guaranteeing that the system operates at the optimal conditions [28]. In particular, feed flow and hydrodynamic conditions promote the adhesion of particles to the membrane in most of the desalination processes used at an industrial level [27].…”

“…When dealing with the filtration of organic matter, the water permeation through the membrane causes the fast formation of a fouling layer, Based on Choi's analysis [29], this comes from the compulsive transport of foulants into the membrane surface by the drag force of permeate flow, which leads to the sealing of pores provoking the fouling layer. Likewise, the moist and low shear environment facilitate the proliferation of bacteria and biofilm formation on the membrane's surface [27].…”

“…Another key factor is the concentration polarization since the concentration of microorganisms and nutrients available in the layer directly affects the adhesion and formation of biofilm. Basically, when these elements increase their concentration, the rate of biofouling will increase as well [27]. When the carbon concentration increases in the bulk solution, this can contribute to obtaining higher rates of biofouling, which increases the mass of organic matter (such as microorganisms) present in the biomass [27].…”

“…Basically, when these elements increase their concentration, the rate of biofouling will increase as well [27]. When the carbon concentration increases in the bulk solution, this can contribute to obtaining higher rates of biofouling, which increases the mass of organic matter (such as microorganisms) present in the biomass [27]. At this point, the element related to the attachment of microorganisms, as well as other organic compounds in the concentration polarization layer, is the lack of convective flow near the membrane surface [27].…”