Potencial de Reaproveitamento do Concentrado da Osmose Inversa do Programa Água Doce – Bahia/Brasil Como Solução Osmótica no Processo de Osmose Direta

Abstract

The Programa Água Doce (PAD) aims to ensure permanent and sustainable access to high-quality drinking water through desalination systems that employ Reverse Osmosis (RO) technology. This technology, however, generates reverse osmosis concentrate (ROC), a potentially polluting by-product. The present study adopted a quantitative methodological approach based on experimental investigation using primary data. The general objective was to evaluate the potential reuse of ROC generated by RO desalination units of the Água Doce Program (PAD) in Bahia, Brazil, as a draw solution in a Forward Osmosis (FO) system. Specifically, the study sought to: (i) assess pollutant removal through the FO process using ROC as the draw solution; (ii) optimize FO system operation under conditions where ROC is used as the draw solution; and (iii) investigate the salinity profile of the draw solution resulting from FO system operation and its potential reuse. The results showed that, after ROC characterization and during 264 hours of operation, the permeate flux progressively decreased, reaching an average value of 2.7 L/m²·h. The reverse salt flux remained relatively constant, although some peaks outside the linear trend were observed, with an average of 6.3 g/m²·h. The average conductivity decreased from 27.67 mS/cm to 15.92 mS/cm. Scanning Electron Microscopy (SEM) analyses revealed that the new membrane exhibited a uniform and unaltered morphology, with no evidence of fouling. In contrast, the used membrane showed precipitated salt deposits on its surface, which led to a reduction in water flux from 3.89 L/m²·h to 2.83 L/m²·h. Experiments performed with methylene blue (MB) dye showed a 98% rejection rate, demonstrating the efficiency of the Forward Osmosis (FO) process. It can be concluded that the use of ROC as a draw solution (DS) is feasible and advantageous, particularly when diluted and reused from concentrates generated in RO desalination systems.