STRUCTURAL FEATURES OF HUMIC ACIDLIKE SUBSTANCES FROM SEWAGE SLUDGES

We studied humiclike fractions from aerobic and anaerobic sewage sludges. Elementary and functional group analysis showed that these fractions had lower C and total and carboxyl acidity and higher H, N, and phenolic acidity than soil humic acids (HA). The main groups revealed by infrared study were aliphatic, ─CH3, and ─CH2groups, and peptide linkages of proteins and polypeptides. The13C-NMR solution spectra indicated that ─CH2in long alkyl chains predominated in these fractions, although appreciable branching might also occur in the hydrocarbon chains. Gas chromatography and mass spectrometry revealed that n-alkanes and linear, unsaturated, and branched fatty acids were abundant in the persulfate digest. Dicarboxylic and fatty acids were the most abundant compounds of the permanganate digest, the latter being, probably, the structural basis of the sludge humic acids. © 1990 Williams & Wilkins.