Comparison of CTA and TFC FO-membranes for water recovery

Abstract

For centuries, mankind has faced water-related issues for it is a limited good of vital importance for human development. Climate change, pollution and world water scarcity now have given more awareness to these problems. However, it is in human societies nature to consume water and return it to the environment in a form that is no longer profitable for human use. Ages of developing techniques and systems for water distribution has led to nowadays being able to obtain water from our own wastewater. Osmotic membrane bioreactor (OMBR) processes are a very important step in water tertiary treatment and furthermore, forward osmosis OMBR (FO-OMBR), which is at the vanguard of research and innovation. FO-OMBR uses the water gradient that the difference of osmotic pressure creates to separate physiochemically water from wastewater. In this project, first steps at laboratory-scale experiments are carried out to characterize osmotic membranes for further use at pilot-scale. Cellulose triacetate (CTA) has been widely used, and new materials such as thin-film composite (TFC) polyamide membranes have been produced. Therefore, new work is needed to compare their behavior at different concentration of the osmotic agent while also comparing performances at water recovery, lifespan of membrane and costs. In this work, sodium chloride is used as the osmotic agent. Also, the system configuration is considered as a limiting variable at operating, so different experiments were carried in both suction and pulsion modes. Impact of the pump is contemplated too so different pump speed experiments were held. In this study, it was also considered challenges such as salt loss from the draw solution (DS), so RSD value is reckoned. However, membrane fouling was not contemplated in this study; further work needs to be done. Once the results were obtained, it was regarded that when operated with TFC membrane better performance of the OMBR is done, as RSD values were lower and permeate volumes higher. Even though no essential differences where seen between suction and pulsion configurations, it was pulsion that showed better performance values