ABSTRACT
The textile industry generates large volumes of water characterized mainly by an intense color coming from dyes that are difficult to process due to their synthetic base and the presence of aromatic components. Due to the stricter regulation on the discharge of these effluents, in order to reduce dye waste before discharge into natural channels, alternatives are being sought to manage this wastewater. In this work, the concentration of dyes in simulated wastewater from the textile industry was studied by forward osmosis (with a cellulose triacetate CTA membrane), with the aim of concentrating the dye for its future recovery and reincorporation into the production process. Two dyes of different nature were evaluated to study the efficiency of the proposed process, using NaCl and reverse osmosis brine from a model seawater desalination solution as extraction solutions. It was observed that dye type (reactive or direct) and their charge influence the color rejection with the forward osmosis membrane used. It was able to concentrate the dyes in the feed solution up to approximately 55% with the reverse osmosis brine from the model seawater desalination solution. Finally, the results demonstrate that the FO process is a promising option for concentrating dyes present in wastewater from the textile industry in order to reuse them in the dyeing process.
ABSTRACT
Management of wastewater is a major challenge nowadays, due to increasing water demand, growing population and more stringent regulations on water quality. Wastewaters from food conservation are especially difficult to treat, since they have high salinity and high organic matter concentration. The aim of this work is the treatment of the effluent from a table olive fermentation process (FTOP) with the aim of reusing it once the organic matter is separated. The process proposed in this work consists of the following membrane-based technologies: Ultrafiltration (UF) (UP005, Microdyn Nadir), Forward Osmosis (FO) (Osmen2521, Hydration Technology Innovation) and Nanofiltration (NF) (NF245, Dow). The FO process was implemented to reduce the salinity entering the NF process, using the FTOP as draw solution and, at the same time, to concentrate the centrate produced in the sludge treatment of a municipal wastewater treatment plant with the aim of obtaining a stream enriched in nutrients. The UF step achieved the elimination of 50% of the chemical oxygen demand of the FTOP. The UF permeate was pumped to the FO system reducing the volume of the anaerobically digested sludge centrate (ADSC) by a factor of 3 in 6.5 h. Finally, the ultrafiltrated FTOP diluted by FO was subjected to NF. The transmembrane pressure needed in the NF stage was 40% lower than that required if the ultrafiltration permeate was directly nanofiltered. By means of the integrated process, the concentration of organic matter and phenolic compounds in the FTOP decreased by 97%. Therefore, the proposed process was able to obtain a treated brine that could be reused in other processes and simultaneously to concentrate a stream, such as the ADSC.
