Fractionation of soluble microbial products (SMP) and soluble extracellular polymeric substances (EPS) from wastewater sludge

Abstract

Dissolved organic matter (DOM) in soluble microbial products (SMP), loosely bound (LBEPS) and tightly bound extracellular polymeric substances (TBEPS) were extracted from wastewater sludge, fractionated by size exclusion chromatography and characterized by ultraviolet absorbance at 230, 254 and 280 nm, the dissolved organic carbon (DOC) content and excitation-emission-matrix (EEM) spectra. The DOM of molecular weight (MW) > 20000 Da accounted for 33% of SMP, including proteins of high aromaticity, and 22% of both LBEPS and TBEPS, which were composed of organic acid-like substances and proteins, respectively. Polyaluminum chloride (PACI) coagulation effectively removed this DOM fraction. Conversely, the DOM of MW < 1000 Da were mostly non-aromatic organic acids (and possibly polysaccharides) of low aromaticity for SMP and both EPS, and removal by PAC1 coagulation was minimal. The findings indicated that the chemical characteristics of DOM in SMP and LBEPS were similar but not identical. The TBEPS and LBEPS exhibited significantly different DOM based on DOC distribution or EEM fingerprint.