Removal of fluorescent dissolved organic matter in biologically treated textile effluents by NDMP anion exchange process: efficiency and mechanism.

The efficiency and mechanism of anion exchange resin Nanda Magnetic Polymer (NDMP) for removal of fluorescent dissolved organic matter in biologically treated textile effluents were studied. The bench-scale experiments showed that as well as activated carbon, anion exchange resin could efficiently remove both aniline-like and humic-like fluorescent components, which can be up to 40 % of dissolved organic matter. The humic-like fluorescent component HS-Em460-Ex3 was more hydrophilic than HS-Em430-Ex2 and contained fewer alkyl chains but more acid groups. As a result, HS-Em460-Ex3 was eliminated more preferentially by NDMP anion exchange. However, compared with adsorption resins, the polarity of fluorescent components had a relatively small effect on the performance of anion exchange resin. The long-term pilot-scale experiments showed that the NDMP anion exchange process could remove approximately 30 % of the chemical oxygen demand and about 90 % of color from the biologically treated textile effluents. Once the issue of waste brine from resin desorption is solved, the NDMP anion exchange process could be a promising alternative for the advanced treatment of textile effluents.

Characterization of dissolved organic matter in municipal wastewater using fluorescence PARAFAC analysis and chromatography multi-excitation/emission scan: a comparative study.

Dissolved organic matter (DOM) in municipal wastewater was mainly characterized using high-performance liquid chromatography (HPLC) and size exclusion chromatography (HPSEC) with multi-excitation/emission fluorescence scan. Meanwhile, fluorescence excitation-emission-matrix combined with parallel factor analysis (EEM-PARAFAC) was also applied. Compared with chromatography fluorescence fingerprints, the EEM-PARAFAC model could not reflect the variety of DOM species with similar fluorescence but different physicochemical properties. The chromatography results showed that the protein-like species were variable among different municipal wastewater treatment plants, some of which are in combination with humic-like species; while there were two major humic-like species fractionated by hydrophilicity and molecular weight (MW), which are also the major contributors to UV absorbance at 254 nm. It was also identified that the relatively hydrophilic humic fractions were slightly larger than the relatively hydrophobic humic fractions. In all the investigated wastewater treatment plants, the relatively hydrophilic and larger MW humic fraction mainly contributed to the fluorescence intensity of humic-like EEM-PARAFAC components. As well as facilitating interpretations of EEM-PARAFAC components, the HPLC/HPSEC fluorescence fingerprints also contributed to a better understanding of fluorescent DOM species in municipal wastewater.

HPLC/HPSEC-FLD with multi-excitation/emission scan for EEM interpretation and dissolved organic matter analysis.

The need to track and characterize dissolved organic matter (DOM) has made fluorescence excitation-emission matrix (EEM) spectroscopy extensively used. In this work, reverse phase high-performance liquid chromatography (RP-HPLC) and high-performance size exclusion chromatography (HPSEC) with fluorescence detector (FLD) were used for EEM interpretation and DOM analysis. Given that fluorescence detectors can scan with multi-excitation or multi-emission mode, HPLC-FLD with multi-excitation scan directly verified the prevalence of multi-peak fluorophores in EEM, which provides a corrective insight for the current fluorescence regional integration (FRI) methods; whereas HPLC-FLD with multi-emission scan provided more informative fluorescence fingerprints for identification of DOM species, which is a chromatographic surrogate for determining the proper number of PARAFAC components. Besides providing a deep insight for the current EEM interpretation, the HPLC/HPSEC-FLD results also directly related physiochemical properties to DOM species, including polarity and molecular weight (MW) distribution, which is helpful for further characterization their behavior in water and wastewater treatment process. A chromatography technique with multi-excitation and multi-emission fluorescence scan can be an informative method for EEM interpretation and DOM identification and characterization.