Optimization of Coagulation-Flocculation with Aluminum Sulfate for the Treatment of Chemical Industry Effluent

Abstract Industrial activities require large volumes of water for production processes and for washing equipment, containers, and facilities, generating effluents whose physicochemical characteristics often prevent their direct discharge into receiving water bodies. The treatment and management of industrial wastewater are therefore essential to comply with regulatory standards and minimize environmental impacts. In this context, this study presents a treatability assessment of industrial effluent generated by a chemical products industry employing industrial water treatment located in the Caí Valley region (Rio Grande do Sul, Brazil). The objective was to characterize raw and treated effluents and to propose an efficient treatment strategy based on laboratory-scale evaluations. The methodology included production process mapping, physicochemical characterization of raw effluent, coagulation–flocculation experiments using a Jar-Test under different pH conditions and coagulant dosages, and characterization of the treated effluent under optimized operating conditions. The raw effluent exhibited several parameters above regulatory discharge limits, including pH, phosphorus, turbidity, and iron. Considering regulatory requirements and cost-effectiveness aspects, the optimal treatment conditions consisted of 55 mg/L of 50% aluminum sulfate at an initial pH between 8.0 and 9.0. Under these conditions, significant reductions were observed for several parameters, particularly total alkalinity (85.85%), hardness (85.00%), phosphorus (74.51%), and turbidity (69.03%). Overall, the study demonstrates how specific effluent treatability assessments can support the development of optimized physicochemical treatment configurations, contributing to regulatory compliance and reliable industrial wastewater management.