A review on the applicability of integrated/hybrid membrane processes in water treatment and desalination plants

Conventional processes involved in water treatment, either in water treatment plants or reverse osmosis desalination plants, have encountered several obstacles that have severely affected their performances and efficiencies. Pollution of natural water resources, increasing demand and overuse of clean water have all put critical stress on currently available conventional water treatment/desalination plants. Due to these problems, integrated/hybrid membrane processes have attracted much interest. An integrated/hybrid membrane system is a process which combines a membrane filtration unit (microfiltration/ultrafiltration/nanofiltration) with other processes such as coagulation, adsorption and ion exchange. Alternatively, it can be a combination of different membranes in the same system with a conventional process. The purpose of this paper is to review the applicability of integrated/hybrid membrane systems in water treatment plants and reverse osmosis desalination plants. The literature shows that many benefits and marked improvements could be achieved with integrated/hybrid membrane processes, such as enhanced quality of the water produced, energy savings, environmental friendliness, and reductions in the capital and operating costs of the plants. The implications of the integrated membrane system prove that it has huge potential to be widely applied and can lead to a breakthrough in solving the problem of water scarcity. © 2014 Elsevier B.V. All rights reserved.

Integrated/hybrid membrane systems have been shown to be better than conventional systems for water treatment and desalination. However, each water treatment/RO desalination plant might require a different type of combination and pretreatment. This is because the efficiency and complexity of an integrated/hybrid membrane system depends mainly on the quality of the feed water and the specifications of the water to be produced. From the examples of integrated/hybrid membrane systems presented above it can be seen that a good grade of groundwater only requires a simple coagulation–NF system to produce potable water, while poor quality seawater requires more extensive pretreatment prior to reaching the RO system. Thus the study and understanding of membrane fouling mechanisms are very important for the design of integrated/hybrid membrane systems. In most cases, the interactions between foulants or contaminants in the water, the membrane and additives such as coagulants and antiscalants are not well understood. Extensive research and advanced analysis should be carried out to study and investigate mechanisms of fouling caused by reactions among the three substrates mentioned above. Overcoming the fouling issue will lead to a more precise and effective integrated/hybrid membrane system for each specific application in the water industry. This in turn will not only cut the overall expense of the plant, but will also help to reduce energy consumption and minimize the disposal of concentrated waste. Further improvements in the systems will require innovative solutions in which energy and environment are major factors to be considered in designing a plant that will achieve sustainable growth. Acknowledgments The authors wish to gratefully acknowledge the financial support for this work by grant NPRP 5-1425-2-607. The authors also wish to acknowledge the Ministry of Education Malaysia for sponsoring W.L. Ang's postgraduate study via MyBrain.