Aplicação de extrato de sementes de Moringa oleifera na remoção de matéria orgânica por flotação por ar dissolvido

Abstract

It is essential that water from the rivers, used for public supply, has adequate potability. When it is directed to the water treatment plants (WTP) and has excess organic matter, there is the possibility of an increase in the formation of trihalomethanes (THM's), generated in the disinfection stage with chlorine, in the conventional treatment process. The objective of this research was to evaluate the removal of dissolved organic matter by the application of saline extract (CaCl2) from seeds of only Moringa oleifera and associated to polyaluminium chloride (PACI), by dissolved air flotation (DAF), in waters with low turbidity. The efficiency of the processes was evaluated by analyzing the parameters color, turbidity, UV254nm absorbance, dissolved organic carbon and fluorescence spectroscopy. The water used in the study from a river in the region of the Curitiba/PR. In the first stage, analyzes were performed in turbid waters of 10, 20 and 30 NTU, in which coagulation, flocculation and dissolved air flotation (DAF) with Moringa oleifera extracted with CaCl2 in the dosages of 10, 20, 30, 40 and 50 mg L-1, in order to detect the best dosage of the coagulant. The best coagulant dosages were 20, 30 and 40 mg L-1 for water with 10, 20 and 30 NTU, respectively. In the second moment, PAC addition in the best dosages of the Moringa oleifera, in the ranges of 10 to 30% substitution of the saline coagulant. The utilization of coagulants in the proportion of 70:30 (M. oleifera:PAC) led to removal efficiencies above 85% for turbidity, 95% for color and 40% for compounds with UV254nm absorbance. The COD increase in water was lower, as the amount of Moringa oleifera used was decreased. By Spectroscopic fluorescence, it can be observed that the use of the associated coagulants provided reductions of intensity in the wavelenghts range excitation and emission of 225/400 nm (Tryptophan), respectively, when a greater amount of PAC was used, and increase of intensity in the wavelengths of 220-325 nm (Tyrosine), respectively, according to the increase of higher dosages of Moringa oleifera - due to the organic matter coming from the natural coagulant. Therefore, the efficiency of the process in the formation of THM’s was evaluated. It was verified that the use of the coagulant Moringa oleifera, as well as the use of this coagulant associated to the PAC, did not result in a large generation of THM’s in the system, remaining below the limit of 100 μg L-1. Thus, it was possible to conclude that the associated use of Moringa oleifera and PAC coagulants at low dosages may be a promising alternative for turbid water up to 30 NTU.