Organic Compounds of Natural Origin in Sludge from Waste-Water Treatment Plant

Organic compounds of natural origin were analyzed in three types of sludge produced by waste water treatment plant - limed sludge with 12 % of CaO, limed sludge with 6% of CaO and sludge without processing. Analysis was performed by pyrolytic gas chromatography with mass spectrometry detection (Py-GC/MS). The main component pf natural origin in waste-water treatment sludge were determined. They comprise compounds form the following groups: fatty acids and their methylesters, steroids, substances derived from polysaccharides, substances derived from lignin, compounds with nitrogen (both heterocyclic and aliphatic), substances with so called non-specific origin (toluene, styrene, acetic acid, methylphenols and phenols). Interpretation was attempted for identification of organic compounds sources as well as determination of humification and mineralization degree. The ratio benzene/toluene was used as the criterion for humification in waste-water treatment sludge. Benzene is derived from degradation of condensed aromatic structure, toluene is derived from both condensed aromatic structures and pseudostable organic matter. The ratio furfural/pyrolle was used of expression of mineralization degree of organic matter. Furfural is a product of labile organic matter (saccharides) while pyrolle originates from stable organic matter (humified components containing nitrogen). Compared with non-limed sludges, limed sludges have higher rate of decomposition of organic matter as well as subsequent mineralization. Limed sludges accumulate more compounds derived from lignine which is caused by more intensive decomposition of polysaccharides. From the point of view of utilization in agriculture, limed sludge is the most suitable sludge produced by waste-water treatment.