Direct contact ultrasound for fouling control and flux enhancement in air-gap membrane distillation

Naji, Osamah and Al-juboori, Raed and Bowtell, Les and Alpatova, Alla and Ghaffour, Noreddine (2020) Direct contact ultrasound for fouling control and flux enhancement in air-gap membrane distillation. Ultrasonics Sonochemistry, 61. pp. 1-12. ISSN 1350-4177

Abstract

Air Gap Membrane distillation (AGMD) is a thermally driven separation process capable of treating challenging
water types, but its low productivity is a major drawback. Membrane fouling is a common problem in many
membrane treatment systems, which exacerbates AGMD’s low overall productivity. In this study, we investigated
the direct application of low-power ultrasound (8–23 W), as an in-line cleaning and performance boosting
technique for AGMD. Two different highly saline feedwaters, namely natural groundwater (3970 μS/cm) and RO
reject stream water (12760 μS/cm) were treated using Polytetrafluoroethylene (PTFE) and polyvinylidene
fluoride (PVDF) membranes. Theoretical calculations and experimental investigations are presented, showing
that the applied ultrasonic power range only produced acoustic streaming effects that enhanced cleaning and
mass transfer. Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy (ATR FT-IR) analysis
showed that ultrasound was capable of effectively removing silica and calcium scaling. Ultrasound application
on a fouled membrane resulted in a 100% increase in the permeate flux. Cleaning effects accounted for around
30–50% of this increase and the remainder was attributed to mass transfer improvements. Contaminant rejection
percentages were consistently high for all treatments (> 99%), indicating that ultrasound did not deteriorate the
membrane structure. Scanning Electron Microscopy (SEM) analysis of the membrane surface was used to confirm
this observation. The images of the membrane surface demonstrated that ultrasound successfully cleaned the
previously fouled membrane, with no signs of structural damage. The results of this study highlight the efficient
and effective application of direct low power ultrasound for improving AGMD performance.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 July 2013 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 July 2013 -)
Date Deposited: 24 Jan 2020 00:49
Last Modified: 07 Feb 2020 01:52
Uncontrolled Keywords: Membrane distillation; Direct ultrasound; Fouling control; Cleaning; AGMD; Challenging feedwater; Mass transfer
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090509 Water Resources Engineering
09 Engineering > 0906 Electrical and Electronic Engineering > 090699 Electrical and Electronic Engineering not elsewhere classified
Socio-Economic Objective: D Environment > 96 Environment > 9611 Physical and Chemical Conditions of Water > 961101 Physical and Chemical Conditions of Water for Urban and Industrial Use
Identification Number or DOI: 10.1016/j.ultsonch.2019.104816
URI: http://eprints.usq.edu.au/id/eprint/37403

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