Desaguamento de lodo de ETA com a utilização de Leito de Drenagem

During the stages involved in the water treatment process, sludge forms, which is characterized as solid waste and, therefore, its destination must be compatible with the guidelines of the PNRS Law 12.305/2010, prioritizing reduction, reuse and recycling . In this sense, dewatering, understood as a method of reducing the volume of sludge, meets the requirements established by the National Policy on Solid Waste. Dewatering is characterized by the removal of free water, supernatant found in the interstices of solids, using natural or mechanical systems. Drainage beds, designated as LD and previously conceptualized as drying beds, are among these natural systems. Thus, the main objective of this study was to evaluate the efficiency and quality of sludge dewatering from an ETA that uses aluminum sulfate as a coagulant, with a fixed solids concentration of 2% applied to the LD system. For that, a bench scale LD prototype was used in order to simulate sludge dewatering, using three sludge layer heights (h=10, 30 and 50 cm) and two non-woven geotextiles as a filtering layer of mass. per unit area of 400 and 600 g/m2, named GTNT400 and GTNT600. These assays were conducted in triplicate and the stopping criterion established was 72 hours. The analyzes performed on the filtrate (apparent color, turbidity and pH) followed the methods recommended by APHA/AWWA/WEF (2001). It was also performed the moisture content (w) of the sludge and the mass retained in the geotextile (MR). The analysis of the results showed that lower solids application rates (TAS) removed water in a shorter time and the higher the hydraulic load, the longer the removal time. The GTNT600 showed the best behavior, promoting greater sludge removal, with an increase in free water drained and better quality of the drained. Higher heights (hydraulic loads) promoted an increase in drainage time.