Study on the Effectiveness of Two Biopolymer Coagulants on Turbidity and Chemical Oxygen Demand Removal in Urban Wastewater

The present study investigated the effectiveness of two biopolymer coagulants on turbidity and chemical oxygen demand removal in urban wastewater. The biopolymers were produced from vegetal biomass using the mucilage extracted from Opuntia robusta cladodes, and Uncaria tomentosa leaves. Opuntia robusta is an abundant species in Mexico, which is not edible. Uncaria tomentosa is an exotic invasive species in Mexico and other countries, which negatively affects the ecosystems where it is introduced. A combined experimental design of mixture–process was selected to evaluate the effectiveness of both biopolymer coagulants regarding aluminum sulfate (conventional chemical coagulant). Results showed turbidity and chemical oxygen demand removal efficiencies of 42.3% and 69.6% for Opuntia robusta and 17.2% and 39.4% for Uncaria tomentosa biopolymer coagulant, respectively, at a dose of 200 mg/L. Furthermore, optimum conditions from the experimental design to reach the maximum turbidity and chemical oxygen demand removal were obtained at an Opuntia robusta biopolymer coagulant concentration of 10 mg/L, showing removal efficiencies of 68.7 ± 1.7% and 86.1 ± 1.4%, respectively. These results support using Opuntia robusta as an alternative biopolymer coagulant in urban wastewater treatment.