Characterization of activated sludge in wastewater treatment processes using front-face excitation–emission matrix (FF-EEM) fluorescence spectroscopy

Abstract

A rapid, reliable assay and on-line monitoring for activated sludge have always been urgently demanded in wastewater treatment processes. In this work, front-face fluorescence excitation–emission matrix (FF-EEM) spectroscopy was employed for in situ analyzing activated sludge suspension. The results indicated that the fluorescence of activated sludge samples could be successfully characterized by using FF-EEM spectroscopy. Protein-like substances, nicotinamide adenine dinucleotide (NADH), and humic-like substances in the FF-EEM of activated sludge correlated well with mixed liquid volatile suspended solids (MLVSS, R² = 0.8834, p-value < 0.01), intracellular NADH (R² = 0.9488, p-value < 0.001), and humic-like substances in soluble microbial products (SMP, R² = 0.8430, p-value < 0.01), respectively. Protein-like substances and NADH in the FF-EEM may serve as good indicators for biomass and bioactivity of activated sludge, respectively. The fiber optic FF-EEM on-line measurement was quite stable at various probe immersion depths (when >10 cm) and various floc sizes, but aeration intensities varied fluorescence signals. FF-EEM fluorescence spectroscopy was demonstrated to be promising in fast analysis and on-line monitoring of activated sludge.