Evaluation the efficiency of individual organic coagulants and associated with aluminum sulfate in the removal of colloidal substances from Rio Doce, Minas Gerais, Brazil

Abstract

The conventional water treatment process, involving primary, secondary, and tertiary stages, frequently employs chemical coagulants like aluminum sulfate during coagulation/flocculation. However, this practice generates residues with high concentrations of harmful inorganic salts, posing environmental and operational challenges. This study investigates the use of natural organic coagulants as sustainable and effective alternatives, emphasizing their potential to reduce residual inorganic content and leverage resources already present in the environment. Water samples from the Rio Doce in Santana do Paraíso, MG—impacted by the 2015 Fundão tailings dam collapse (SAMARCO)—were treated using Jar-test equipment to simulate coagulation/flocculation and sedimentation processes. The performance of aluminum sulfate, Tanfloc SG, and Moringa oleifera Lam was evaluated for turbidity removal, color reduction, and pH stability. While aluminum sulfate achieved 92 % turbidity and 83 % color removal, the natural coagulants demonstrated competitive results: Tanfloc SG achieved 83 % turbidity and 70 % color removal, and M. oleifera Lam achieved 75 % turbidity and 65 % color removal. Remarkably, combining aluminum sulfate with M. oleifera enhanced removal efficiencies to 99 % for both turbidity and color, with minimal pH variation. The findings highlight the advantages of natural coagulants, including lower residual inorganic waste and the opportunity to repurpose environmentally available resources, making them a promising alternative to conventional aluminum-based coagulants. This approach contributes to more sustainable water treatment practices, particularly for areas impacted by environmental disasters.