Influência de múltiplos fatores no desaguamento de lodo de ETA em leitos de drenagem

Abstract

The sludge generated in Water Treatment Plants (WTP) has a high moisture content, normally greater than 95%, and is considered to be solid waste according to Law 12,305/2010, which foresees non-generation and reduction of solid waste as priorities, closely followed by reuse and recycling. The volume reduction of WTP sludge can be carried out through dewatering, a process consisting of the removal of free water, which is supernatant and can be found in the interstices of solids, using natural or mechanical systems. Among the natural dewatering systems, Draining Beds (DB) have shown promise, however, the process needs to be further researched. Thus, the main objective of this research was to study the influence of multiple factors, such as sludge solids content, sludge layer height, solids application rate (SAR) and different types of geotextiles, during the free water drainage stage of the dewatering process using DB. For this purpose, a Draining Bed system was built at bench scale, with a total of 335 drainage simulations being carried out, using 6 different types of geotextiles; 6 raw sludge total solids (TS) contents and 5 sludge layer heights. The analysis of the results allowed us to conclude that the stabilization of a pre-filter formed by the sedimentation of solids present in the sludge has an overriding role in the drainage process compared to the role of the different types of geotextiles. It was also concluded that the TS content of the raw sludge has an indirect relationship with the final percentage of drained liquid; the beds with higher SAR had higher percentages of good quality drained liquid and registered longer times until the end of free water flow; the drainage in beds with small sludge layer height and low levels of TS is not very efficient in promoting good quality drained liquids; the filter opening in the geotextile fabric is related to the promotion of drained liquids with high apparent color rates; and the characterization of the different types of sludges, mainly regarding particle size distribution and composition, can influence the drainage process.