Effect of Membrane Fouling on Fertilizer-Drawn Forward Osmosis Desalination Performance.

Majeda Khraisheh,Fares Almomani,Mona Gulied

doi:10.3390/membranes10090243

Abstract

Fertilizer-drawn forward osmosis (FDFO) has garnered immense attention for its application in the agricultural field and its potential to reuse wastewater sustainably. Membrane fouling, however, remains to be a challenge for the process. This study aims to investigate the influence of membrane fouling on the performance of the FDFO process. Synthetic wastewater (SWW) and multi-component fertilizer (MCF) were used as feed solution (FS) and draw solution (DS) with cellulose triacetate (CTA) forward osmosis (FO) membrane orientation. The performance was evaluated through water flux (WF), percentage recovery and percentage of salt reject. The WF declined from 10.32 LMH (L/m2·h) to 3.30 LMH when ultra-pure water as FS was switched with concentration FS indicating the dependence of the performance on the type of FS used. Accelerated fouling experiments conducted to verify the fouling behavior showed a decline in the water flux from 8.6 LMH to 3.09 LMH with SWW and 13.1 LMH to 3.42 LMH when deionized water was used as FS. The effects of osmotic backwashing and in situ flushing as physical cleaning methods of the foul membrane were studied through water flux and salt recovery percentage. Both cleaning methods yielded a WF close to the baseline. Osmotic backwashing yielded better results by eliminating foulant–foulant and foulant–membrane adhesion. The cleaning methods were able to recover 75% of phosphate and 60% of nitrate salts. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) results validated the effectiveness of the methods for the physical cleaning of foul membranes. This study underlines the importance of the FS used in FDFO and the effectiveness of osmotic backwashing as a cleaning method of FO membranes.

Highlights

In times of ever-increasing water scarcity, membrane-based desalination has been sought among the most efficient desalination processes available
The performance of the fertilizer-drawn forward osmosis (FDFO) was first assessed through the initial water flux (WF) of the cellulose triacetate (CTA) Forward osmosis (FO) membrane when the DI water and Synthetic wastewater (SWW) were used as feed solution (FS) and multi-component fertilizer draw solution (MCFDS)
The undeniable advantage of FDFO should not be hindered by the inevitable membrane fouling experienced by the process

Summary

Introduction

In times of ever-increasing water scarcity, membrane-based desalination has been sought among the most efficient desalination processes available. The scaling of membranes shortens the life of the porous material; it hinders efficient operation, leading to increased energy consumption [3,4]. The scaling of membranes is linked to increase in operation and maintenance cost as well [5,6]. Forward osmosis (FO) has garnered immense attention for its application in water desalination, especially as an energy efficient and economical alternative to conventional membrane-based desalination methods. The absence of hydraulic pressure in the process indicates that the FO technology uses osmotic differential for separation across the membrane, unlike RO and NF processes. The osmotic differential causes freshwater molecules to flow from the feed solution to the Membranes 2020, 10, 243; doi:10.3390/membranes10090243 www.mdpi.com/journal/membranes

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