COMPARISON OF THE EFFICIENCY OF FIVE EXTRACELLULAR POLYMERIC SUBSTANCES(EPS) EXTRACTION METHODS USING THREE DIMENSIONAL EXCITATION AND EMISSION MATRIX(EEM) FLUORESCENCE SPECTROSCOPY TOGETHER WITH CHEMICAL ANALYSIS

The efficiency of five extracellular polymeric substances (EPS) extraction methods was compared on normal activated sludge and aerobic granular sludge using three-dimensional excitation and emission matrix (EEM) fluorescence spectroscopy. Three chemical methods (EDTA, formaldehyde, formaldehyde plus NaOH), one physical method (cation exchange resin) and a control method (high speed centrifugation) were tested. Five fluorescence peaks were identified in EEM fluorescence spectra of the EPS samples. Two peaks were attributed to the protein-like fluorophores, two peaks were attributed to the fulvic-like fluorophores and one peak to the humic-like substance.Homogenization is absolutely necessary for the extraction of EPS from aerobic granular sludge.Formaldehyde interfered with DNA content determination. Extract residues should be removed from EPS by dialysis membrane filtration to avoid EPS contamination. Compared with the other four methods, the extraction ability of high speed centrifugation was relatively ineffective; the CER method was a correspondingly effective method which was gentler and did not cause cell lysis; although the formaldehyde plus NaOH method was most effective in extracting EPS, the quantity of DNA was the highest. EPS contamination due to NaOH and EDTA was pointed out by EEM fluorescence spectroscopy analysis.