Adam Hambly

Fluorescence as a potential monitoring tool for recycled water systems: a review.

A rapid, highly sensitive and selective detector is urgently required to detect contamination events in recycled water systems - for example, cross-connection events in dual reticulation pipes that recycle advanced treated sewage effluent - as existing technologies, including total organic carbon and conductivity monitoring, cannot always provide the sensitivity required. Fluorescence spectroscopy has been suggested as a potential monitoring tool given its high sensitivity and selectivity. A review of recent literature demonstrates that by monitoring the fluorescence of dissolved organic matter (DOM), the ratios of humic-like (Peak C) and protein-like (Peak T) fluorescence peaks can be used to identify trace sewage contamination in river waters and estuaries, a situation analogous to contamination detection in recycled water systems. Additionally, strong correlations have been shown between Peak T and biochemical oxygen demand (BOD) in rivers, which is indicative of water impacted by microbial activity and therefore of sewage impacted systems. Hence, this review concludes that the sensitive detection of contamination events in recycled water systems may be achieved by monitoring Peak T and/or Peak C fluorescence. However, in such systems, effluent is treated to a high standard resulting in much lower DOM concentrations and the impact of these advanced treatment processes on Peaks T and C fluorescence is largely unknown and requires investigation. This review has highlighted that further work is also required to determine (a) the stability and distinctiveness of recycled water fluorescence in relation to the treatment processes utilised, (b) the impact of matrix effects, particularly the impact of oxidation, (c) calibration issues for online monitoring, and (d) the advanced data analytical techniques required, if any, to improve detection of contamination events.

Organic matter fluorescence in municipal water recycling schemes: Toward a unified PARAFAC model

Organic matter (OM) is a ubiquitous constituent of natural waters quantifiable at very low levels using fluorescence spectroscopy. This technique has recognized potential in a range of applications where the ability to monitor water quality in real time is desirable, such as in water treatment systems. This study used PARAFAC to characterize a large (n=1479) and diverse excitation emission matrix (EEM) data set from six recycled water treatment plants in Australia, for which sources of variability included geography, season, treatment processes, pH and fluorometer settings. Five components were identified independently in four or more plants, none of which were generated during the treatment process nor were typically entirely removed. PARAFAC scores could be obtained from EEMs by simple regression. The results have important implications for online monitoring of OM fluorescence in treatment plants, affecting choices regarding experimental design, instrumentation and the optimal wavelengths for tracking fluorescent organic matter through the treatment process. While the multimodel comparisons provide a compelling demonstration of PARAFACs ability to distill chemical information from EEMs, deficiencies identified through this process have broad implications for interpreting and reusing (D)OM-PARAFAC models.

Fluorescence monitoring at a recycled water treatment plant and associated dual distribution system--implications for cross-connection detection.

Dual distribution systems are becoming increasingly common in greenfield housing developments in Australia for the redistribution of recycled water to households for non-potable use. Within such schemes there exists the potential for cross-connections between recycled and drinking water systems. Due to the high level of recycled water treatment, these events are unlikely to lead to outbreaks of illness in the community. Nonetheless, they do represent a breach of the recycled water risk management strategy and therefore an elevated level of risk to consumers. Furthermore, cross-connection events have the potential to undermine public confidence in these types of water recycling. A rapid, highly sensitive method of cross-connection detection may therefore provide an additional level of confidence in these schemes. The aim of this research was to determine the potential for using fluorescence spectroscopy as a monitoring tool in water treatment plants and dual distribution systems. Samples from both the water recycling plant and dual distribution system were collected on a weekly basis over 12 weeks. Fluorescence excitation-emission matrix (EEM) spectra and water quality parameters including dissolved organic carbon, UV(254), pH, conductivity, free chlorine and turbidity were obtained for each sample. The fluorescence EEM spectra of recycled and drinking water were distinctly different and exhibited low variability throughout the course of the sampling program, indicating a degree of stability of the fluorescent components within the organic matter. A ten-fold difference in mean fluorescence intensity was observed for recycled water compared to drinking water, which was greater than the difference observed for the other measured water quality parameters. Probabilistic analysis was used to determine the reliable detection limit of recycled water contamination of drinking water. Accounting for the inherent variability of both recycled water and drinking water, a 45% contamination of recycled water in drinking water could be detected with a signal-to-noise ratio greater than 3 for more than 95% of individual random sample pairs. Greater sensitivity can be assured by averaging numerous samples. In comparison, a 70% contamination of recycled water in drinking water was required for the same detection using conductivity.

Characterising organic matter in recirculating aquaculture systems with fluorescence EEM spectroscopy

The potential of recirculating aquaculture systems (RAS) in the aquaculture industry is increasingly being acknowledged. Along with intensified application, the need to better characterise and understand the accumulated dissolved organic matter (DOM) within these systems increases. Mature RASs, stocked with rainbow trout and operated at steady state at four feed loadings, were analysed by dissolved organic carbon (DOC) analysis and fluorescence excitation-emission matrix (EEM) spectroscopy. The fluorescence dataset was then decomposed by PARAFAC analysis using the drEEM toolbox. This revealed that the fluorescence character of the RAS water could be represented by five components, of which four have previously been identified in fresh water, coastal marine water, wetlands and drinking water. The fluorescence components as well as the DOC showed positive correlations with feed loading, however there was considerable variation between the five fluorescence components with respect to the degree of accumulation with feed loading. The five components were found to originate from three sources: the feed; the influent tap water (groundwater); and processes related to the fish and the water treatment system. This paper details the first application of fluorescence EEM spectroscopy to assess DOM in RAS, and highlights the potential applications of this technique within future RAS management strategies.

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

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, UV(254), 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 lambda(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 (lambda(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.

Cross-connection detection in Australian dual reticulation systems by monitoring inherent fluorescent organic matter

New housing developments are now commonly incorporating dual reticulation water systems for the redistribution of recycled water back to households for non-potable use. Within such distribution systems is the potential for cross-connections between recycled and drinking water pipelines, and a number of such events have been documented both in Australia and internationally. While many cross-connections are unlikely to present a source of health concern given the high level of recycled water treatment, they do have the potential to negatively impact public confidence in dual reticulation systems. A rapid and highly sensitive method of cross-connection detection is required to increase consumer confidence in the construction and maintenance of such recycled water distribution systems. This paper reviews a number of current and potential cross-connection detection methods, highlighting the use of fluorescence spectroscopy as a highly promising analytical tool for portable cross-connection detection.

Probabilistic analysis of fluorescence signals for monitoring dual reticulation water recycling schemes

Improved techniques are required for the detection of inadvertent cross-connections between recycled water and potable water systems in dual reticulation schemes. The aim of this research was to assess the potential for fluorescence spectroscopy to be developed as a tool to distinguish recycled water from potable water. Weekly grab samples of recycled and potable water were obtained over 12 weeks from within an Australian dual reticulation site and analysed for fluorescence excitation-emission matrix (EEM), dissolved organic carbon (DOC), electrical conductivity (EC), and pH. Probabilistic techniques including distribution function fitting and Monte Carlo simulation were used to assess the ability to distinguish between recycled water and potable water sample pairs and the reliability of doing so. Fluorescence EEM spectroscopy was determined to be the most effective for the reliable differentiation by monitoring the protein-like fluorescence at peak T(1)--an excitation-emission wavelength pair of λ(ex/em)=300/350 nm. While EC could distinguish between recycled and potable water, it was shown to be less sensitive and less reliable than peak T(1) fluorescence.

Application of portable fluorescence spectrophotometry for integrity testing of recycled water dual distribution systems.

Water utilities supplying recycled water to households via a “third-pipe” or “dual reticulation” system have a need for a rapid, portable method to detect cross-connections within potable water reticulation networks. This study evaluates portable fluorimetry as a technique for cross-connection detection in the field. For the first time, an investigation of a full-scale dual reticulation water-recycling network has been carried out to identify cross-connections using a portable fluorimeter. We determined that this can be carried out with a 3 mL water sample, and unlike methods that are currently in use for cross-connection detection, can be achieved quickly without disruption to water flow or availability within the network. It was also revealed that fluorescence trigger values could be established with high levels of confidence by sampling less than 2.5% of the network. Fluorescence analysis was also able to uncover a single, real cross-connection event. As such, this paper is a fundamental demonstration of fluorescence as a reliable, highly portable technique for cross-connection detection within dual reticulation water recycling networks and further establishes the abilities of fluorescence devices as valuable field instruments for water quality monitoring.