THE RHEOLOGY OF SEWAGE-SLUDGE AT DIFFERENT STEPS OF TREATMENT

Rheological parameters are very important in sewage sludge management, not only as designing parameters in transporting, storing, landfillin g and spreading operations, but also as controlling ones in many treat ments, such as stabilisation and dewatering. To study how different tr eatments affect sludge rheological behaviour, research has been undert aken at CNR-Istituto di Ricerca Sulle Acque (CNR-IRSA), and the prelim inary results are discussed in this paper. Sludge samples taken from t hree municipal wastewater treatment plants at different steps of treat ment have been tested by a rotational viscometer and data interpreted through both Bingham plastic and Ostwald pseudoplastic models. Coeffic ients of those models have been then correlated to solids concentratio n. Results confirmed that solids concentration is the main parameter a ffecting sludge rheology and evidenced that a single parameter is not sufficient to represent the rheological behaviour, thus indicating tha t other parameters should be introduced and characteristics considered for a better understanding of the phenomenon. (C) 1997 IAWQ. Publishe d by Elsevier Science Ltd.