Sistema de pré-tratamento convencional seguido de eletrodiálise aplicados à simulação da dessalinização de águas salobras

Abstract

The scarcity of available water has generated the need to use alternative sources of water for public supply. The objective of this work was to evaluate the efficiency of the bench system by batch in the treatment by coagulation, flocculation, sedimentation and filtration (CFS-F) followed by electrodialysis (ED) in the treatment of brackish water, in order to propose an alternative for desalination. The brackish water (affluent in the proposed treatment system) had concentrations of 1000, 2000 and 3000 ±180mg.L-1 of total dissolved solids (TDS). The pretreatment consisted of CFS-F using polyaluminium chloride as a coagulant, the dosage was previously adjusted by Jar Test assays. After the pre-treatment, PCCell ED200 model ED equipment was used, where the TDS were directed from the diluted to the concentrate, obtaining desalted water (diluted effluent) and waste or concentrated water (concentrated effluent) after the ED. The CFS-F removed total suspended solids (20.02 to 99.99%), turbidity (78.13 to 98.45%) and apparent color (85.05 to 99.99%) and there was always a reduction in pH of the water after this treatment, with average pH values for influent (brackish water) from 7.22 to 8.08 and for effluent from 6.43 to 7.26. However, in CFS-F there was no change in the concentration of TDS, being considered an adequate system to be applied before the ED. The ED was efficient in reducing 90.01, 94.78 and 96.73% of TDS from the dilute for influent concentrations of 1000, 2000 and 3000 ±180mg.L-1 of TDS, respectively. To obtain diluted effluent by the proposed system with a TDS concentration lower than 100mg.L-1

, a longer treatment time it was observed for the higher TDS concentrations flowing into the ED. However, the greater the SDT of dilute and concentrated inflow, the greater the corresponding electric current when applying a constant voltage of 30V. This shows that the TDS concentration inside the ED equipment influences the electric current that, in turn, increases the ion flow rate from the dilute to the concentrate, easing the treatment time factor for the higher influent TDS concentrations. Regarding the pH, after treatment by ED, an average pH of 8.62 to 8.75 it was observed for the diluted and from 5.31 to 8.77 for the concentrate.