Applying synchronous fluorescence with Gaussian band fitting and MW-2DCOS to assess removals of DOM in acrylic fiber wastewater treatment process

Abstract

Acrylic fiber wastewater (AFW) with hypertoxicity and recalcitrant are treated by advanced oxidation biological techniques. Some water quality parameters as online indicators to monitor pollutant removals, fail to trace removals of organic pollutants. Hence a practicable tool is indispensable for insight into removals of organic pollutants. Synchronous fluorescence spectroscopy (SFS) combined with Gaussian band fitting and two-dimensional correlation spectroscopy (2D-COS) was developed to evaluate removals of dissolved organic matter (DOM) fractions in an AFW treatment plant. Five fluorescence components were identified from DOM by SFS with principal component analysis and Gaussian band fitting, i.e., low-molecular-weight (LMWF1 and LMWF2), microbial humic-like (MHLF) and high-molecular-weight substances (HMWF1 and HMWF2). LMWF2 and HMWF2 were the representative components (52.96%) in the AFW, whose removal efficiencies (94.05% and 73.11%) were much higher than those of LMWF1 (40.16%) and HMWF1 (17.45%). Nitriles and amides occurred in LMWF2, whereas the aromatics in four DOM fractions. Based on 2D-COS, the changing order of DOM fractions was MHLF→ HMWF1→ nitriles→ LMWF2→ HMWF2→ amides→ LMWF1→ aromatics. The nitriles and HMWF1 were continuously removed in treatment process. LMWF2 was degraded by anaerobic and nitrifying bacteria, while the degradation of amides and HMWF2 by anaerobic and aerobic microorganisms. Furthermore, the nitriles could reduce microbial activities, which was mainly removed with the degradation of LMWF2. SFS combined with Gaussian band fitting and 2D-COS could be an applicable approach to monitor variations of DOM fractions and evaluate its removals in the AFW. These findings could be conducive to developing an online equipment in WWTP.