Potencial valorização do lodo de estação de tratamento de esgoto como matéria prima para produção de blocos cerâmicos

Abstract

Sewage sludge is an extensively produced residue directly related to population growth and economic development. Wastewater treatment plants generate sewage sludge classified as a not dangerous residue class II-A (not inert) according to NBR 10004 (2004a), which is commonly discharged in sanitary landfills. An alternative for the destination of this residue is the use as raw material in the production of red ceramics, in which low contents (< 5%) enable the obtainment of products with good quality and comparable to those currently available. Thus, this study aimed to evaluate the effect of adding sewage sludge to clay used as raw material in the production of structural ceramic blocks. Different contents of sewage sludge were used replacing clay (from 0% to 15% in dry weight), and the water content was adapted based on variations of the rheological behavior for each mix. The optimized mixtures were utilized to produce ceramic blocks by extrusion in a reduced scale (1:5). Physical and mechanical characteristics of the blocks after firing were analyzed, such as dimensional stability, water absorption, bulk density, and compressive strength, and the results were evaluated considering the limits recommended by Brazilian standards. The mixtures with sewage sludge exhibited a reduced elastic response, which affected the extrusion process; consequently, they required more water. The values of total linear shrinkage after drying and firing and water absorption obtained were within the limits established for ceramic blocks for all the sludge contents utilized. The compressive strength results of the blocks also indicated that up to 15% of sludge can be incorporated into clay mixtures to produce extruded ceramic blocks.