EVOLUTION OF ORGANIC-MATTER IN SEWAGE-SLUDGE - A STUDY BASED ON THE USE OF HUMIFICATION PARAMETERS AND ANALYTICAL ELECTROFOCUSING

The degree of humification (DH), humification index (HI), and humifica tion rate (HR) were determined for seventeen samples of sewage sludges and composts from sewage sludges. The same samples, extracted with 0. 5 m NaOH, 0.1 m Na4P2O7, and 0.1 m Na4P2O7 adjusted to pH 7, were anal yzed with analytical electrofocusing (EF). The results clearly show th at the organic matter changes much more quickly during composting than during the anearobic digestion. It was also found that the ability of the alkaline solutions to solubilize the organic complexes was greate r the higher the apparent isoelectric point and the greater the reprod ucibilty of the analytical electrofocusing data.