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.
Reverse osmosis is a membrane‐based separation technology, which was developed in the late 1950s and early 1960s, with rapid advancements in the technology through the 1980s. A highly effective and cost‐efficient technology, reverse osmosis is used industrially for desalination of seawater and brackish water, wastewater recovery and reuse, municipal drinking water treatment, and other applications.
Membrane materials and types of modules used in reverse osmosis, as well as theoretical and operational aspects, general design considerations, and economics are reviewed in this article. A discussion of membrane transport theory, flux‐limiting conditions caused by concentration polarization, and membrane fouling is also included.
The recorded history of membrane‐based separations can be traced back to the mid‐eighteenth century, when Abbe Nollet “observed” the phenomenon of osmosis. Over 100 years later, Fick formulated his Law of Diffusion through membranes (which is still today considered fundamental to understanding membrane transport). However, little other substantive development work with membranes was undertaken prior to the early 1900s, and efforts after the turn of the century were focused primarily on microfiltration. It was not until the mid‐twentieth century that membranes and membrane‐based technologies began to flourish.
In the 50 + years since then, development of synthetic membranes has resulted in a number of membranes, varieties and applications. Membranes have been prepared from an assortment of organic (polymeric) and inorganic (ceramic) materials, and have been used for such diverse separations as gas from gas; gas from liquid; liquid from liquid; dissolved solids from liquid; and suspended solids from liquids.
This article chronicles the development of membrane materials, from early efforts using microfiltration to culture bacteria, through the prolific growth of membranes in the latter half of the twentieth century, to the advent of nanotechnology in polymeric and ceramic membranes. In addition to details about membrane materials, preparation methods, and modularization techniques, the drivers for development are discussed.
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