ETUDE DE LA DÉSHYDRATATION DES BOUES EN FONCTION DE L'ETAT D'ACTIVITE DE LA BIOMASSE

Abstract

An essential aspect of the operation of activated sludge systems is the separation of biological solids from the liquid phase and subsequent dewatering of these biosolids. Separation results from the settling of spontaneously aggregated bacteria into flocs. A subsequent dewatering step is usually necessary to achieve a reduction in sludge volume for easier transport and handling, or to minimize the space or energy required for drying or incineration. Dewatering is one of the most difficult and costly processes in wastewater treatment. Typically, dewatering is carried out physically using mechanical methods such as vacuum filtration, belt filter presses, drying beds and centrifugation. The choice of technique depends mainly on the type of sludge and the space available. The efficiency of the dewatering process is highly dependent on the nature of the sludge. In many cases, chemical conditioning agents are required to improve dewatering. Unfortunately, in some cases these agents are overused, producing a chemically contaminated sludge that prevents its use as compost on agricultural land. This thesis project will take an in-depth look at the effect of microbial activity on sludge dewatering, which is closely linked to operating conditions in wastewater treatment plants (WWTPs). Studies will be carried out under optimal operating conditions, as well as under various malfunctioning conditions. The aim of the thesis project is to explore the impact of microbial activity on dewatering. The study has been extended by examining this influence on urban sludge, mixed sludge resulting from biological treatment of mixed water (urban and industrial water), as well as digested and fermented sludge from methanization and bio-hydrogen production processes.