Fouling Monitoring Techniques for Water Treatment Membrane Processes

Membrane fouling and flux decline are undesirable, albeit inevitable, problems in membrane filtration processes for water treatment. The development of low fouling membranes, the design of high efficiency modules, the selection of optimal operational strategies, and several improvements made in peripheral control, monitoring, and cleaning techniques have been adopted to deal with these formidable obstacles. Unfortunately, the slow development of these methods has limited the competitiveness and subsequent acceptance of membrane water treatment processes in the last three decades. An early warning technique for the determination of fouling problems in water treatment membrane processes is crucial to the improvement of membrane process operation, as well as to the development of a fouling prevention strategy. Severe flux decline and process failure are usually observed if the quality of the produced water fails a given set of standards. This is the most expensive method for fouling monitoring, but is still widely adopted due to its practicality. Recently, researchers have become more aware of the importance of in situ, online monitoring of fouling growth. Several in situ monitoring techniques have been developed in the laboratory to reveal the growth mechanism of fouling layers in membrane filtration processes. Nevertheless, few process-oriented, reliable, and predictable online monitoring techniques for onsite fouling analysis and control exist. In this study, an integrated, online monitoring technique that provides dynamic and real-time information of a fouling process has been developed. This monitoring technique has been preliminarily demonstrated for water treatment membrane processes using a photosensor array. The application to a water treatment membrane spearation unit with a photosensor array to provides real time, 3D profiling of fouling layer thickness changes. Using sensor array that are able to scan membranes surface on demand, an integrated, online, and dynamic monitoring technique would be feasible for direct application to commercial membrane modules for water treatment. The results of the online dynamic analysis suggest that this technique provides in situ measurement of fouling layer thickness, dynamic analysis of the fouling layer structure, and monitoring of water quality during the membrane filtration process. Moreover, it is notable that many available, robust, fouling monitoring devices have never moved beyond laboratory status. Significant challenges remain to improve available monitoring techniques to effectively bridge the gap between the laboratory setting and field application.