Diagnosis of the destination of sludge from Sewage Treatment Plants in the metropolitan region of Porto Alegre: an analysis in light of the National Solid Waste Policy

Abstract

The management of sludge generated at Wastewater Treatment Plants (WWTPs) represents one of the main environmental and operational challenges in the basic sanitation sector. This study aimed to evaluate the final disposal of sludge produced by 28 WWTPs in the Metropolitan Region of Porto Alegre in 2024, based on the guidelines of the National Solid Waste Policy (PNRS). Data were obtained through the analysis of environmental licensing processes available in the Online Licensing System (SOL) of Henrique Luis Roessler State Foundation for Environmental Protection (FEPAM-RS), focusing on the treatment technologies adopted, the volume of sludge generated, and the information contained in the Waste Transport Manifests (MTRs), which record the final destination of the waste. The results indicated that only 8 WWTPs carried out sludge disposal during the analyzed period, with approximately 89% of the total volume sent to sanitary landfills. Although still common, this practice contradicts the principles of the PNRS, which prioritizes the valorization of solid waste through alternatives such as composting and agricultural reuse. Noteworthy are successful initiatives by public companies such as SABESP-SP and SANEPAR-PR, which demonstrate the feasibility of transforming sludge into Class A fertilizer, generating environmental, agronomic, and economic benefits. It is concluded that progress is needed in sludge management in the Metropolitan Region of Porto Alegre, to ensure environmentally sound disposal and the valorization of this waste, following the PNRS.