Extraction of extracellular polymeric substances from activated sludge using sodium oxalate |
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| Authors: | M Sajjad K S Kim |
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| Institution: | 1.Korea University of Science and Technology,Daejeon,Republic of Korea;2.Environmental Engineering Research Division,Korea Institute of Civil Engineering and Building Technology,Goyang-Si,Republic of Korea |
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| Abstract: | In this study, sodium oxalate was employed to extract extracellular polymeric substances (EPS) from activated sludge samples. The optimum dose of sodium oxalate was 1.34 g/g VSS (volatile suspended solids), and the extraction time was 60 min at pH 7. The total EPS contents obtained under the optimized conditions were approximately 191 mg/g VSS, and they predominantly consisted of proteins, polysaccharides and humic substances. The extraction efficiencies of the chosen method for the major biopolymers were 39, 43 and 410 % higher compared with the ethylenediaminetetraacetic acid (EDTA), cation exchange resin and control methods. Cell lysis measured in terms of deoxyribonucleic acid, and unidentified EPS were approximately 50 % lower in the sodium oxalate method than in the NaOH and EDTA methods. The EPS composition and the ratio of proteins/polysaccharides (1.38–2.21) were extremely dependent on the operating conditions maintained during the extraction. The inductively coupled plasma spectroscopic results demonstrated that the release of divalent metals, such as Ca2+ and Mg2+, from the sludge matrix was directly correlated with higher EPS extraction efficiencies in the sodium oxalate protocol. Moreover, the precipitation of Ca2+ and Mg2+ as metallic oxalates disrupted the floc structure and subsequently enhanced the EPS recovery. Fourier transform infrared studies revealed the presence of functional groups due to EPS molecules in all extracted samples. |
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