Potential and limitation of fluorescence-based membrane integrity monitoring (FMIM) for reverse osmosis membranes

In wastewater recycle for potable purposes, virus removal is the most critical issue from the public health stand point. Therefore, the regulatory agency sets minimum virus removal efficiencies that must be met by combining multiple treatment processes. In most potable reuse processes, reverse osmosis (RO) plays a critical role by removing salts, viruses, dissolved organic matters, etc. It has been reported that RO removes viruses at over 6 log efficiencies, but it receives no more than 2 log credits from regulatory agencies due to the lack of sensitive integrity monitoring technologies better than conductivity-based technologies. In recent years, fluorescence-based membrane integrity monitoring (FMIM) has drawn special attention because of its simplicity, capability of continuous monitoring, and the high resolution. Lab and field studies have shown FMIM can provide around 4 log resolution for commercially available RO membranes. In this study, potential and limitation of current FMIM technology are reviewed. Further, ideas to improve the resolution beyond 4 log are suggested.