Study of ultrafiltration and reverse osmosis membrane processes for advanced treatment and recycling of textile effluent in Bangladesh

Abstract

Textile and apparel industries are the major role-players in the fast-growing economy of Bangladesh. However, the textile sector consumes a large amount of water for various wet processing operations, and hence, has a high water-footprint. Currently 98% of the water used by local textile factories is groundwater, which is causing depletion of ground water levels at a high rate.Considering the gravity of groundwater crisis in future, Bangladesh Government and international brands and retailers are advocating local textile factories to reuse textile effluents and implement ZLD (zero liquid discharge) option in the upcoming years. However, the existing study about the technical and investment aspects of using advanced treatment technologies does not provide enough insights for reusing textile effluents or implement ZLD. In this work, the performance of ultrafiltration and reverse osmosis was studied as advanced treatment processes for recycling textile effluents of Bangladesh. For advanced treatment, a mobile setup of ultrafiltration (UF) and reverse osmosis (RO) unit was used at six selected factory premises to further treat ETP(effluent treatment plant) treated water. The advanced treatment was carried out for three different permeate to reject flowrate ratios to observe changes in the permeate and reject water quality and contaminants removal efficiency. A time dynamic analysis wasalso done to further demonstrate the performance of advanced treatment of conventional ETP treated water of a denim washing factory.The corresponding technical and economic issues of water recycling and reusing were also analyzed.The study showed that the treated water quality was well within the standards of groundwater quality that is being used as process water in the local factories.It also showed that it was possible to reduce blue water footprint up to 80% based on the operating configuration of the RO unit. It also demonstrated that it was possible to reduce grey water footprint from 154.6 m3/day (7.4%) to 15568.6 m3/day (95%) for the selected industries. Finally, the study showed that the advanced water treatment cost by ultrafiltration and reverse osmosis ranged from 24.06 BDT/m3to 24.29 BDT/m3for the selected textile industries.