Year

2020

Degree Name

Master of Research

Department

School of Civil, Mining and Environmental Engineering

Abstract

Forward osmosis (FO) is a membrane separation technique which utilizes osmotic pressure as the driving force to draw pure water through a semi permeable membrane. A draw solution with a higher osmotic pressure than the feed solution creates an osmotic pressure differential, driving water permeation. FO is gaining increasing interest in wastewater treatment and significant opportunities exist in pre-concentrating complex wastewaters (such as digester sludge centrate) for water, nutrient and energy recovery. Inherently, FO has a low fouling potential, greater fouling reversibility and high selectivity making it the most viable technology for pre-concentration thus facilitating nutrient recovery for commercial usage such as agricultural fertilizers production. It is also of interest particularly in wastewater purification for re-use purposes where the concentration of nutrients plays a vital role in determining the water quality which otherwise would cause eutrophication in rivers or lakes. FO integration with anaerobic membrane bioreactors has demonstrated great potential due to high rejections of most contaminants. FO stands out through enabling a double barrier approach for subsequent recovery of pure water by coupling with reverse osmosis (RO), nanofiltration (NF) or membrane distillation (MD). The concentration of nutrients in anaerobically digested sludge centrate are quite high and present an opportunity for nutrient recovery. Previously developed techniques like RO, NF, ion exchange etc. for concentrating nutrients are either energy intensive or expensive to operate and maintain. FO has a notably high rejection of phosphate (up to 99%), which is essential for ecology, food industry and agricultural purposes. A relatively lower rejection (50-90%) of ammonia nitrogen is however a key challenge to be addressed.

This thesis examined the effect of membrane fouling on the retention of nutrients along with the impacts of critical operating parameters (i.e. water flux and water recovery) on the rejection performance of FO process. In addition, key aspects of the FO process including, effective membrane area, reverse salt flux (RSF) and operation time with respect to their influence on ammonia nitrogen rejection behavior were individually evaluated...

This thesis is unavailable until Wednesday, May 04, 2022

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.