Application of a fluorescence EEM-PARAFAC model for direct and indirect potable water reuse monitoring: Multi-stage ozone–biofiltration without reverse osmosis at Gwinnett County, Georgia, USA

Abstract

Periods of drought coupled with increasing population growth have prompted increased interest in potable water reuse in Gwinnett County, Georgia, USA. However, such inland water recycling facilities are challenged with treatment approaches where reverse osmosis (RO) membrane concentrate disposal is a barrier to implementation of potable reuse. To evaluate alternative treatment processes, testing of two side-by-side pilot systems using multi-stage ozone and biological filtration without RO was conducted to compare indirect potable reuse (IPR) to direct potable reuse (DPR). Two water sources were investigated—influent from Lake Lanier for the IPR pilot, and a blend of 25 % reclaimed water mixed with lake water (75 %) for the DPR pilot. To assess the nature of organic matter removed during potable reuse, excitation–emission matrix (EEM) fluorescence spectroscopy/PARAllel FACtor (PARAFAC) analyses were examined as a fingerprinting tool. The objectives were to determine (a) if a DPR scenario, when preceded by advanced wastewater treatment, could achieve drinking water quality comparable to IPR and (b) if water quality monitoring using EEM/PARAFAC methods could predict results for DPR and IPR water quality, comparable to parameters obtained in a supplementary study that required more expensive, time-consuming, and complicated analytical techniques. Sample scores representing relative concentrations of fluorescing organic matter derived from the EEM-PARAFAC model decreased in the order of reclaimed water > lake water > DPR pilot > IPR pilot, demonstrating that EEM/PARAFAC could distinguish between DPR and IPR water quality. An assessment of a comprehensive list of individual organic compounds (reported separately) validated that blend ratios of 25 % reclaimed water, or higher mixed with lake water (75 %) did not meet primary and secondary drinking water standards. Likewise, in this study, EEM/PARAFAC analysis demonstrated the 25 % blend did not provide drinking water quality indicating this simple, inexpensive method could be used for potable reuse monitoring.