Aplicação de coagulantes orgânicos extraídos do cacto (Opuntia cochenillifera) e da Moringa oleifera no tratamento de água

Abstract

The purpose of this work was to use organic coagulants (Moringa oleifera and Opuntia cochenillifera) in coagulation, flocculation and sedimentation processes for water supply. Water samples were collected from Tibagi River, located in the North of Paraná. Both organic coagulants were used separately and in combination to compare efficiencies. A study was carried out to determine the removal of turbidity and apparent color, and the behavior of total dissolved solids, electrical conductivity and pH. It was verified after the pre-test that the best concentrations for the coagulant extracted from Moringa oleifera seed in saline solution were C1: 2.5 mg.L-1; C2: 5 mg.L-1; C3: 7.5 mg.L-1. For the coagulant of the cactus Opuntia cochenillifera, the best concentrations were C4: 1 mg.L-1; C5: 2 mg.L-1; C6: mg.L-1 followed by the concentrations of extractive solutions C7: 2.5 mg.L-1; C8: 5 mg.L-1; C9: 7.5 mg.L-1. For the assays made with the combination of both coagulants, half (50%) of the dosages of the coagulants and the extractive solution were used. The treatment was done with the jar test equipment with the same speed gradient and fast and slow mixing times used in the SANEPAR ETA. Correction of pH of the samples was required to analyze the performance of organic coagulants at different pH levels. Up to 100% of the color and 93% of the turbidity were removed using Moringa oleifera. Using the Opuntia cochenillifera cactus, the color and turbidity removal were up to 67% and 39%, respectively. With the two coagulants associated, the color and turbidity removal were up to 96%. The highest values of electrical conductivity were presented in the assays with higher dosage of coagulants. Total dissolved solids increased in all assays due to the dissociation of organic matter and salts from the organic coagulants. The pH did not change in the course of the processes using Moringa oleifera and coagulants in association, but for Opuntia cochenillifera cactus, the pH of all assays increased during the processes. According to statistical analysis, the best values for each single variable were for C2 (5 mg.L-1), neutral pH and 20 minutes of sedimentation using Moringa oleifera and C5 (2 mg.L-1), C8 (5 mg.L-1), neutral pH and 20 minutes of sedimentation using Opuntia cochenillifera cactus. For the association of these two coagulants, the best values were 2.5 mg.L-1of Moringa oleifera, 1 mg.L-1 of Opuntia cochenillifera and 2.5 mg.L-1 of extractive solution with neutral pH and 20 minutes of sedimentation. The results confirm the efficiency of Moringa oleifera in saline solution and show that Opuntia cochenillifera cactus has great potential as a coagulant but require further studies with different dosages of coagulant and different extractive solutions. In relation to the efficiency of the two coagulants together, it is concluded that the association of the two is not viable since only Moringa oleifera ends up performing high removals of color and turbidity.