INVESTIGATION OF INCINERATION CHARACTERISTICS OF WASTE-WATER TREATMENT-PLANT SLUDGE

Incineration is an important disposal method for the large volumes of sludge produced by industrial and municipal waste water treatment. This paper describes analytical methods developed for examining industrial sludge incineration processes and the dependence of potential products of incomplete combustion (PICs) on the sludge composition. A surrogate sludge was developed from peat, calcium and iron salts, and a waste water-treatment polymer suspension to simulate incineration characteristics of the real sludge while allowing for controlled variation of its composition. Experiments were conducted under both oxidative and pyrolysis conditions, in reactor systems ranging from microscale up to bench scale with on-line analytical instrumentation. The organic products emitted from the surrogate were quite similar to those of the sludge, with the exception of products from certain synthetic polymers. Significant quantities of aromatic hydrocarbons were emitted from the combustion of the cellulosic and lignin fractions of the material even without the presence of those specific compounds in the original waste. The presence of the metal salts and the additional water they retained significantly affected the peak hydrocarbon concentration by delaying the onset of emissions and lengthening their duration. The amount of polystyrene and polymethylmethacrylate in the real sludge made their decomposition products important potential PICs, which would need further combustion.