Water Science & Technology—WST Vol 61 No 1 pp 155–162 © IWA Publishing 2010 doi:10.2166/wst.2010.795

Fluorescence monitoring for cross-connection detection in water reuse systems: Australian case studies

A. C. Hambly, R. K. Henderson, A. Baker, R. M. Stuetz and S. J. Khan

A rapid, highly sensitive method for detection of cross-connections between recycled and potable water in dual reticulation systems is required. The aim of this research was to determine the potential of fluorescence spectroscopy as a monitoring tool at three Australian dual distribution (drinking and recycled water) systems. Weekly grab samples of recycled and potable water were obtained over 12 weeks at each site and analysed for fluorescence excitation-emission matrix (EEM) spectroscopy, UV₂₅₄, dissolved organic carbon (DOC), electrical conductivity and pH. Fluorescence EEM spectroscopy was able to differentiate between recycled and potable water at each site by monitoring the protein-like fluorescence at peak T—an excitation-emission wavelength pair of l_ex/em=300/350 nm. While electrical conductivity was also able to distinguish between recycled and potable water, the differentiation was greatest when using fluorescence. For example, the peak T fluorescence in recycled water was up to 10 times that of potable water in comparison with electrical conductivity that had a maximum 5 times differentiation. Furthermore, by comparing the protein-like fluorescence at peak T and humic-like fluorescence at peak A (l_ex/em=235/426 nm), the three different recycled water systems were able to be differentiated. Overall, fluorescence shows promise as a monitoring tool for detecting cross-connections.

Keywords: electrical conductivity; fluorescence EEM; monitoring; public health; recycled water

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