Characterization of fulvic acids contained in municipal sewage purified with activated sludge

Abstract

FA discharged from the wastewater treatment plant were extracted from purified effluents for the quantitative and qualitative analysis. The treated sewage from municipal treatment plants was acidified to pH <2 and extracted with ion exchange resins in a laboratory column. After desorption with NH4OH, the fulvic acids were condensed under vacuum and tested for mass performance, UV-VIS light spectra, IR absorption spectra, elementary composition and other elements. Their structure was analysed and compared to FA present in surface waters and in sewage treated in other sewage treatment plants based on the authors’ own research and the literature data. The concentration of FA in the treated sewage was 5.2 mg/L. There is a high interdependence between the IR spectrum analysis in the visible light and the elementary composition of FA extracted from different environments, confirming the conclusions pertaining to the structure and properties of the acids being tested. The longer sewage is subjected to a biological treatment process, the greater the degree of aromatic condensation and humus maturity of the FA contained within it. FA contained in the sewage treated in the three biological sewage treatment plants have the ratio A2/A3 (the ratio of the absorbance of light with the wavelength of 250 and 300 nm) equal to the value 1.7. There is a high interdependence between the IR spectrum analysis in the visible light and the elementary composition of FA extracted from different environments, confirming the conclusions pertaining to the structure and properties of the acids being tested.