Fluorescence spectroscopy and parallel factor analysis as a dissolved organic monitoring tool to assess treatment performance in drinking water trains

Abstract

Fluorescence excitation emission matrix (FEEM) spectroscopy was used to evaluate its applicability as a tool to track dissolved organic matter (DOM) in a drinking water treatment plant (DWTP) that incorporates a conventional line (consisting in ozonation and GAC filtration) and a membrane-based line (consisting in ultrafiltration, reverse osmosis and mineralization) working in parallel. Seven sampling points within the different process stages were characterized monthly during 2014. A global Parallel Factor Analysis (PARAFAC) was used to pull out underlying organic fractions from the fluorescence spectra. Accordingly a five components model was selected to describe the system and the pros and cons of the model were discussed by analysis of the residuals. Among the five fluorescent components, those associated to humic-like matter (C1, C3 and C4) showed a similar season variability in the river water feeding the DWTP (which resembled that of UV and TOC), whereas the two components associated to protein-like matter (C2 and C5) exhibited a different behavior. The maximum fluorescence intensity values (Fmax) were used to quantify DOM removals across the plant. Compared to the conventional line, water from the UF/RO membrane-based line showed between 6 and 14 times lower fluorescence intensity signal for the humic-like components and between 1 and 3 for the protein-like components as compared to the conventional line. The differences in DOM composition due to seasonal variations and along the treatment trains point out the suitability of using fluorescence measurements over other parameters such as UV as a monitoring tool to help optimize operation conditions of each treatment stage and improve produced water quality in a DWTP.

Fluorescence characterization of organic matter and fouling: Case study in a full‐scale reverse osmosis membrane treatment plant

“…In a full-scale RO plant study, the "microbial by-product-like" fluorescence signals in the brine were most correlated to fouling (Choi et al, 2014). Vera et al (2017) demonstrated the applicability of EEM-PARAFAC fluorescence signals to track organic fractions throughout conventional and membrane treatment at a full-scale plant. The treatment plants incorporated in the Vera et al (2017) study used river water as influent, and the results identified seasonal variations in the fluorescence measurements and tracked changes in organic matter composition throughout treatment.…”

“…As discussed previously, RO permeate samples were excluded from the PARAFAC analysis because they showed almost no fluorescence signal. Vera et al (2017) also found greatly reduced fluorescence signals in the RO effluent because the RO membrane was responsible for removing the largest fraction of organic matter. Additionally, the UF permeate and the second stage RO reject samples showed limited fluorescence signal as well.…”

“…Although turbidity, TOC, and conductivity did not correspond to changes in source water quality throughout pretreatment, the broad selection of fluorescence measurements in classifying fouling periods using classification trees (Table 2) suggests that using EEM-PARAFAC component fluorescence intensities could be useful for tracking organic matter changes throughout pretreatment as well. Previous studies have shown that EEM-PARAFAC component fluorescence intensities decrease with additional treatments (Baghoth, Sharma, & Amy, 2011;Shutova et al, 2014;Vera et al, 2017). The more comprehensive organic matter characterization available with fluorescence measurements was expected to better track changes with pretreatment; however, like turbidity and TOC, neither the EEM peak fluorescence intensities nor the EEM-PARAFAC components reliably track organic matter changes throughout pretreatment.…”

Assessing the potential of fluorescence spectroscopy to monitor contaminants in source waters and water reuse systems

“…Benchtop fluorometers, which are considered to be more sensitive than portable fluorescence sensors, have recently been used to characterize organic matter in drinking water [16][17][18][19] with typically low DOC concentrations (up to <1.0 mg L −1 ). Fluorescence analysis with benchtop fluorometers can be a challenge in field settings due to the poor portability of most benchtop instruments and longer times for spectral acquisition compared to portable sensors.…”

Using FEEM-PARACFAC to characterize metabolic organic components from P17 and NOX strains after AOC assay

“…Consequently, the complex DOM can be classified by its fluorescent components (fluorophores). However, the quantification of the total amount of organic matter for each fraction is still not solved, indicating that previous calibration should be conducted [19].…”