Detecting human sourced contamination in surface water catchments using fluroescent whitening compounds and simple flurometers

The presence of human faecal contamination in surface water catchments is one of the greatest concerns to water managers as it poses potential public health and environmental risks to consumers and users of water. This study was conducted to evaluate the potential effectiveness of the use of fluorescent whitening compounds (FWCs) measured with simple fluorometers to track human sourced contamination in water. The sole presence of faecal indicator bacteria in water does not provide sufficient information regarding the possible sources of faecal contamination. While traditional faecal indicator bacteria have been used for a variety of reasons, other techniques can assist in determining whether the contamination in surface water is likely to have been derived from human or other animal sources. Identifying whether the contamination is from a human source is important from a public health perspective as there are a number of significant water borne human diseases which may contaminate particularly aquaculture products which are grown in estuaries and may be consumed by humans. Methods developed for human sourced contamination tracking in water include chemical markers of anthropogenic origin such as FWCs, caffeine and pharmaceutical compounds. Like many other molecular markers, FWCs, which are derived from laundry and toilet cleaning detergents, can enter surface water environment from failing on-site wastewater management systems (OWMS) or through licensed discharge from wastewater treatment plants. FWCs are virtually ubiquitous in human sewage and therefore indicative of human sourced contamination to surface water. The FWC molecules are fairly structurally stable with slow rates of environmental degradation. FWCs can be detected using thin layer chromatography (TLC), ultraviolet (UV) light, mass spectrometry (MS), high performance liquid chromatography (HPLC) and spectrofluorometers. They may readily be detected at fairly low concentrations using fluorometry. However, systems like mass spectrometry, HPLC and spectrofluorometers are complicated and need personnel to have advanced training to operate this instrumentation where available, and analysis times may also be slow. The use of cheap, simple monitoring equipment such as fixed wavelength fluorometers can offer simplicity and have shorter turnaround time for sample analysis if used. However, in previous studies, the use of simple fluorometers has been impaired by the potential impacts of background matrix interferences from other fluorescing compounds which may cause spectral interferences, inner filtering and concentration quenching effects during fluorescence measurements. In this study, which entailed laboratory and field studies, two simple fluorometers were optimised in the laboratory and validated against the usual sophisticated methods used for FWC analysis including HPLC and a Cary Eclipse spectrofluorometer. The validated detecting method for FWCs using simple fluorometers was applied to field samples from two case studies in NSW to track human sourced water contamination in conjunction with other established faecal source tracking methods. In this research, the results of optimization have shown that the above stated problems for simple fluorometers can be overcome, and when the optimised simple fluorometers were validated against the usual equipment used like the Cary Eclipse spectrofluorometer, the results were found to be not significantly different (p>0.05). When the results were confirmed with additional HPLC analysis, the correlation coefficient, r² = 0.8247 (Pearson’s correlation) and student t-test, indicated that the results were not significantly different to those obtained using the simple fluorometers. The FWCs detection method using simple fluorometers was applied to environmental samples from various water sources giving FWC concentrations similar to those obtained by other researchers who used more sophisticated analysis methods. The FWC method was also applied to samples from two field studies in New South Wales, in conjunction with other faecal source tracking tools which included faecal sterol analysis, dye tracing and bacterial indicator organisms. Simple fluorometers proved that they can be used along with other tools to track human sourced contamination in surface water. It is, therefore, possible to measure FWCs using simple fluorometers to source track human contamination. The use of simple fluorometers to indicate the presence of human sourced contamination can reduce the cost of water testing and reduce the turnaround times for the samples tested. They can be used by personnel in rural and remote areas where it is not possible to access more sophisticated instrumental methods for fluorescence analysis. However, future studies still need to be conducted across a broader geographic area both in developed/developing countries and urban/rural areas to discover the limitations of working with simple fluorometers and the minimum thresholds for their use. This needs to be done to identify fluorometric “hotspots” of human sourced contamination and to also build up a database of FWCs concentrations in various environmental conditions.