Impact of conditioning substances and filtration pressure on dewatering efficiency of sewage sludge

Abstract

Sludge dewatering is a key element in sludge’s processing and management. Solid-phase separation, sludge volume reduction and the separation of a high-quality supernatant are the main tasks of the dewatering devices. The effectiveness of this task, in turn, results from the selection of the dewatering method and conditioning of the sludge before dewatering. The aim of the research was to determine the influence of conditioning substances (polyelectrolyte, fly ash and zeolite) on the efficiency of dewatering at variable filtration pressure. The use of polyelectrolyte in sludge conditioning was a solution that increased the efficiency of the filtration process. On the contrary, the use of structure-forming substances (fly ash and zeolite) slows the process but reduces the hydration of the filter cake. The same trends were obtained in dual conditioning combining dosing of polyelectrolyte and ash or zeolite. It was also shown that the dewatering efficiency of conditioned sludge with these two different substances (ash and zeolite) was the same. The use of zeolite in independent or dual conditioning was important for the quality of the supernatant.