Using Fluorescence Spectroscopy for Improved Water Treatment Resiliency
- Allison Reinert, Erik Rosenfeldt, Ben Wright - Hazen and Sawyer
While robust treatment of raw source water is vital to the multiple barrier approach to providing safe drinking water treatment, many chemicals are poorly removed by conventional treatment processes that are focused on turbidity, natural organic matter, and pathogens. As such, utilities are becoming more interested in identifying strategies that can effectively mitigate negative consequences of acute and chronic spills on water treatment plants (WTPs), finished water quality, and customers. In recent years, several different technologies have been used to monitor and track spill events, but fluorescence spectroscopy has gained traction as one of the promising technologies for spill detection. As such, the principal objective of this presentation will be to present the use of 3-D fluorescence spectroscopy to develop a method for detecting hydrocarbon-based spills as well as an emergency deployment of the fluorometer for real-time early warning and spill detection in a Virginia River following a crude oil spill event.
In order to improve lead time for responding to a spill, utilities and river basin organizations have implemented early warning systems to detect chemical contamination before it reaches utility intakes. Many of the techniques used are based on fluorescence spectroscopy. As such, intensive fluorescence sampling and method development was completed for a utility in Maryland to ascertain if fluorescence was a viable hydrocarbon detection technique given their background water matrix. Bench-top results from the fluorescence work completed by Hazen and Sawyer were compared to commercially available fluorometers. Through the course of the method development, hydrocarbon signatures were detected in water containing natural organic matter (NOM) as well as deionized water. This confirmed that NOM did not interfere with hydrocarbon detection via fluorescence. Also additional testing was done to identify the specific excitation/emission wavelength pairs that identified four specific hydrocarbons. Lastly the detection limits for low-concentration contamination were developed for the four different hydrocarbons. Most hydrocarbons were able to be observed in natural waters from 0.02 to 2 ppm. The work developed for the Maryland utility was then put into action in an emergency deployment situation for a river contamination event upstream of a Virginia utility. Based on the fluorescence sampling conducted at the raw water intake in 15 minute intervals, this particular utility was able to maintain operation for several hours longer than initially expected following the spill.
Both the development of the fluorescence detection capabilities and the deployment of the flourometer for spill detection illustrate the beneficial nature of early warning detection technology to provide monitoring of spills. As source waters become more stressed and as water plants have more pressure to provide the optimum water quality, improving plant resilience to chemical or petroleum spills is of the utmost importance.
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