Valorisation of sewage sludge humic compounds in the aspect of its application in natural environment

The valorization of sewage sludge (SS) has been presented originating from four wastewaters treated in wastewater treatment plants (WWTPs) located in the Wielkopolska province. In the SS samples collected in two successive years, the quantity and quality of humic substances (HSs), fulvic and humic acids (FAs, HAs), amounts of organic carbon (TOC), organic matter (OM), labile carbon (CL), and water extracted organic carbon (WEOC) were determined. It was investigated how the defined parameters depend on the size of the installation and select those which in a routine SS analysis facilitate rapid assessment of their quality and suitability for application in the natural environment. Regardless of WWTP size and the year of analysis, SS was characterized by a significant share of easily decomposable compounds such as FAs and WEOC. The statistical analysis showed significant usefulness of CL, FAs, and HAs in the evaluation of SS quality and usability.