NMR study of the humification process during sewage sludge treatment

Humic acids, extracted from sludge at the biologic–mechanical sewage treatment plant in Jastrzebie Zdroj, have been investigated by means of 1H, 13C and 31P NMR spectroscopy. Sludge samples for studies were taken from the primary settling tank, the nitrification chamber, the digestion chamber and the sludge drying beds.The 1H NMR analysis of humic acid extracted from sludge at various stages of sewage treatment confirmed the presence of the functional groups that are characteristic for humic substances, and the analysis showed changes in their relative intensities. The 13C NMR indicated that the aromatisation of the humic acid increased during sewage treatment. Moreover, the analysis of the 31P NMR spectra allowed us to observe the changes in the phosphorus groups of the studied humic acids.