UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
Water Res. 2010 Oct;44(18):5323-33. doi: 10.1016/j.watres.2010.06.003. Epub 2010 Jun 19.
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.
双分配系统在澳大利亚的绿地住房开发中越来越普遍，用于将再生水重新分配给家庭用于非饮用水用途。在这些计划中，存在再生水和饮用水系统之间交叉连接的可能性。由于再生水的处理水平很高，这些事件不太可能导致社区爆发疾病。尽管如此，它们确实代表了对再生水风险管理策略的违反，因此对消费者构成了更高的风险。此外，交叉连接事件有可能破坏公众对这类水再循环的信心。因此，快速、高灵敏度的交叉连接检测方法可能为这些计划提供额外的信心。本研究的目的是确定荧光光谱学作为水处理厂和双分配系统监测工具的潜力。每周从再生水厂和双分配系统收集样本，共收集 12 周。对每个样本进行荧光激发-发射矩阵（EEM）光谱和水质参数（包括溶解有机碳、UV（254）、pH 值、电导率、游离氯和浊度）的测定。再生水和饮用水的荧光 EEM 光谱明显不同，在整个采样过程中表现出低变异性，表明有机物中荧光成分具有一定的稳定性。与饮用水相比，再生水的平均荧光强度相差十倍，大于其他测量水质参数的差异。概率分析用于确定饮用水中再生水污染的可靠检测限。考虑到再生水和饮用水的固有变异性，在超过 95%的随机样本对中，信号噪声比大于 3 时，可以检测到饮用水中再生水 45%的污染。通过平均大量样本可以保证更高的灵敏度。相比之下，使用电导率检测饮用水中再生水 70%的污染需要相同的检测。
