Characterization of sludge from water treatment plants (WTP) and its use in red ceramic

Resumo

This work presents the principal results of studies about sludge from decantation ponds of water treatment plants (WTP) in the Presidente Prudente-SP (Brazil) region. Initially the sludge was submitted to physical, chemical and mineralogical characterization. As this residue is generated by soil erosion in upstream locations, its grain-size distribution (silt, sand and clay) was studied throughout the year. Also evaluated was the influence of different chemical products used during the flocculation process. Finally, the effects of its incorporation on the properties of ceramic mass were determined. The characterization (TGA, DSC, DTA, XRD, particle size analysis and AAS) showed that this residue hás variable composition according to the WTP localization, the month of sludge production and the chemical used for flocculation. Technological tests (linear shrinkage, water absorption, flexural strength, and apparent porosity and density) of ceramic probes showed that depending on the temperature of firing and the sludge concentration, the measured values can be in accordance with the accepted limit values for the production of bricks. The sludge flocculated with aluminum chemicals was more deleterious than that obtained by using chemicals with iron. The results indicate that WTP sludge can be incorporated in raw materials used to produce red ceramics.