Investigation and development of novel forward osmosis membranes for wastewater applications

Victoria Sanahuja-Embuena

    Research output: Book/ReportPh.D. thesis

    33 Downloads (Pure)

    Abstract

    Membrane technology is globally used for water treatment and one of the many vital technologies used for mitigating water scarcity in the world. Industrialization and globalization have exacerbated the water scarcity and its treatment around the world, and both developing and developed countries are facing these problems. As such, there is a vast interest and resources, from private and public entities, allocated for research on membrane technology.

    Investigation of a new membrane process, forward osmosis (FO), as a water treatment process has been on the raise in the last decades. FO is – in contrast to the common reverse osmosis (RO) process - a pressure-less membrane process, that uses a chemical potential gradient as the driving force for water purification. Thus, this process requires a highly concentrated solution, known as draw solution, to transport water from the feed solution through the semipermeable membrane. Studies on FO have been divided either on the process optimization or the membrane development. This thesis focuses on both types of studies using only hollow fiber forward osmosis membranes (HFFO), and the research is presented in chapters 3-5.

    Chapter 3 presents the investigation of the FO process and FO solute rejection using HFFO modules in a pilot-scale system. A variety of operating conditions were analyzed for the FO process. Internal concentration polarization was found as the dominant factor for variations on the FO performance (water flux and reverse solute flux). Additionally, rejection comparison between FO and RO was examined under identical conditions with the same HFFO module. Higher feed solute rejection was obtained with the use of the FO process, in comparison to the RO. The draw agent and the reverse solute flux seemed to hinder the diffusion of feed solutes across the membrane, enhancing the FO forward rejection.

    Chapter 4 describes the development of the novel HFFO membranes for feed solutions with high fouling potential. A lab-scale module of a HFFO membrane with the selective layer on the outer-surface of the fiber was developed and optimized by using an aquaporin-based additive. Commercial and customized membrane supports were successfully used for developing these membranes. Furthermore, a large inner diameter (0.5-1.1 mm) HFFO membrane was developed and upscaled using commercially available membrane supports. Coating process was adapted for the development of these membranes depending on the characteristics of the supports. The work revealed the importance of the aqueous phase drying during the fabrication, which affects the interfacial polymerization, thus the resulting polyamide layer. The research successfully evolved from 5 different HFFO membranes in labscale size ( < 0.5 m2) to 2 HFFO membranes in pilot-scale size (3 and 5 m2, respectively).

    Finally, Chapter 5 presents the performance of a lab-scale HFFO module with a large inner diameter of 0.8 mm during application. An osmotic membrane bioreactor (OMBR) in a side stream configuration was used as the chosen application. The treated feed solution was an olive mill wastewater, referred as alpechin, chosen due to its complexity and organic load. A one-month operation of the OMBR using the newly developed HFFO membrane demonstrated the feasibility of this application. The pollutant rejection was kept high (75%-99%) and FO membrane integrity and performance was maintained.
    Original languageEnglish
    Place of PublicationKgs. Lyngby
    PublisherDTU Environment
    Number of pages208
    Publication statusPublished - 2021

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