Pre-treatment

Pre-treatment plays a significant role in maximising the efficiency of the preferred desalting technology. The Centre is interested in funding research that improves understanding of the relationship between pre-treatment and treatment, and how novel pre-treatment technologies and improvements can reduce fouling and/or scaling of the coupled treatment process. The Centre’s projects in pre-treatment include:

Assessing the biofouling role of microbes in the desalination system; From the intake pipe to the reverse osmosis membranes

Primary Investigator: Dr Sophie Leterme, Flinders University
Research Participants: Flinders University, SA Water
Funded by: National Centre of Excellence in Desalination
Total project value: $1,699,662

This project combines ecological, genomics, molecular and chemical expertise  to assess the role played by microbial communities in biofouling seawater reveres osmosis (SWRO) desalination plants. These microbes 1) have a size ranging from 0.2 to 200 um, 2) posses the potential to secrete extracellular polymeric substances (EPS) and 3) are suspected to be the main cause of biofouling with desalination plants. Our project aims to identify whether the EPS produced/organic matter contained in the microbes are the main source of biofouling in pretreatment and membrane systems. In addition, EPS may be a food source for bacterial populations inside the system. This will be tested under different stress-induced conditions similar to the ones used at the desalination plant in a ‘model operating system’, which will be built in the laboratory using various membranes/filters typically used for SWRO desalination systems. We will then identify which microbes survive within the system, secrete EPS and use them as a source of nutrients for their survival. To facilitate solutions to microbial-induced biofouling,  this project will produce a comprehensive tool for the assessment and management of risk. This will further identify whether biofouling could occur based on 1) the biological and physical characteristics of the feed/cleaning water and the organisms present in the water, 2) the topological structure of the surfaces within the system of the desalination plant, and 3) the internal stresses associated with the operating environment. Ultimately, this will provide further understanding of the biofouling problem and will assist in the development of strategies for future prevention.

Evaluation of non-chemical pulsed power technology as an antifouling pre-treatment for RO desalination membranes

Primary Investigator: Dr Thomas Yeager, Victoria University
Research Participants: AquaMem Scientific Consultants, SA Water
Funded by: National Centre of Excellence in Desalination
Total project value: $350,000

The project will determine the efficacy of a non-chemical approach for prevention of bio-fouling. The proposed process is based on an alternating or pulsed electromagnetic field (EMF) that has been commercially demonstrated to be effective in industrial cooling systems for impeding (or reversing) biofouling and inhibiting scale formation. Laboratory based trials will be used to investigate the effect of the Dolphin pulsed EMF technology on biofilm growth and development, and on microbial populations in seawater.

Membrane adsorption bioreactor hybrid system as a pretreatment to reverse osmosis desalination

Primary Investigator: Prof. S. Vigneswaran, University of Technology Sydney
Research Participants: University of Technology Sydney, University of New South Wales, Gwangju Institute of Science and Technology, Singapore Membrane Centre, King Abdullah University of Science and Technology
Funded by: National Centre of Excellence in Desalination
Total project value: $490,000

In this study, we will design an environmentally friendly cost-effective pretreatment process of membrane adsorption bioreactor hybrid system through a detailed fundamental study followed by semi-pilot studies in Sydney and Korea. We will optimise its design in terms of reduction of organic and biofouling. This pretreatment will be a sustainable alternative to chemically-intensive seawater reverse osmosis (SWRO) pretreatment in removing particulate and microbial, and organic micro-pollutants. It is robust, eliminates the use of chemicals, and requires little maintenance and energy. It produces a biostable RO feed which is applicable to both urban and remote coastal seawater desalination systems. It can be retro-fitted into existing plants and can reduce the carbon footprint.

Membrane flocculation hybrid system as pre-treatment to brackish water reverse osmosis desalination system: Emphasis on chemical use reduction and recovery

Primary Investigator: Prof. S. Vigneswaran, University of Technology Sydney
Research Participants: University of Technology Sydney, State Water, Coliban Water, Steri-flow Filtration Systems
Funded by: National Centre of Excellence in Desalination
Total project value: $670,000

This project will establish and evaluate a novel immersed membrane flocculation hybrid pre-treatment system as an effective pre-treatment to RO membrane separation processes. It will be a compact and robust, energy efficient pre-treatment attractive both in large municipal schemes and small water schemes (e.g. to treat brackish water in regions lacking adequate freshwater). Here, the emphasis will be to reduce the use of chemical and their disposal through the selection of alternative chemicals, pre-adsorption and resource recovery from chemical sludge.

Modelling, monitoring and control of RO biofouling

Primary Investigator: Dr Ralf Cord-Ruwisch, Murdoch University
Research Participants: Nanyang Technological University, AquaMem Scientific Consultants, Valoriza, University of Alicante
Funded by: National Centre of Excellence in Desalination
Total project value: $942,000

Biofouling of RO membranes contributes to the costs of the desalination process because of the need for regular membrane replacement. Biofouling is a complex process that involves binding of the membrane by bacterial biofilms feeding on organic contaminants in the feedwater and associated precipitation of organic macromolecules (e.g. biopolymers). This project aims to develop an online biosensor for monitoring of biodegradable contaminants and possibly biopolymers, and a concept computer-controlled biofilm reactor based on the above biosensor that can be used as an RO pretreatment for the removal of organic contaminants, limiting membrane fouling caused by biofilms and possibly also organic colloids.

Non-brittle ceramic hollow fibre membranes

Primary Investigator: Prof. Huanting Wang, Monash University
Research Participants: The University of Queensland
Funded by: National Centre of Excellence in Desalination
Total project value: $1,023,000

This project aims to develop non-brittle ceramic hollow fibre membranes for pre-treatment of seawater in seawater desalination processes. Existing ceramic hollow fibre membranes tend to be brittle, and thus limit their widespread industrial applications. In this proposed research, non-brittle ceramic hollow fibre membranes will be developed via incorporation of ceramic nanofibres into porous ceramic structure. This project is expected to lead to a cost-effective technique for fabrication of ceramic hollow fibre membranes with high toughness and tunable pore sizes for efficient pre-treatment of seawater.

The optimisation and improvement of direct filtration pre-treatment to reduce both organic and bio-fouling of RO membranes

Primary Investigator: Prof. S. (Vigi) Vigneswaran, University of Technology Sydney
Research Participants: ProAlliance, Curtin University, Gwangju Institute of Science and Technology, Singapore Membrane Technology Center, King Abdullah University of Science and Technology, The University of New South Wales
Funded by: National Centre of Excellence in Desalination, ProAlliance
Total project value: $540,000

The pre-treatment direct filtration system feeding the reverse osmosis (RO) unit is used for colloidal fouling reduction and is not efficient in controlling bio-fouling. A number of desalination plants face the problem of bio-fouling of both the cartridge filter and reverse osmosis membranes downstream of the direct filtration system. Traditionally ferric salts have been used as in-line flocculents in deep-bed filtration to remove solids, colloids and dissolved organics present in seawater. We aim to optimise the filtration and flocculation parameters to reduce both organic-fouling and bio-fouling on the RO membranes; identify techniques for evaluating bio- and organic fouling and develop appropriate solutions for direct filtration used as a pre-treatment in order to reduce fouling of RO membranes; and understand the fouling mechanisms on the RO membrane through water and foulant analysis and autopsy of membranes.

Optimising low-pressure membrane pretreatment for desalination

Primary Investigator: Dr Pierre Le-Clech, The University of New South Wales
Research Participants: Curtin University, Siemens, Veolia, Water Corporation
Funded by: National Centre of Excellence in Desalination, Siemens, Veolia, Water Corporation
Total project value: $1,240,000

Low-pressure porous membranes are increasingly considered for pre-treatment of sea and brackish waters. However, membrane fouling remains a major drawback, as it results in high operating, maintenance and cleaning costs. This project aims to better understand and to optimise the strategies currently used for fouling control. The relative efficiencies of both physical and maintenance chemical cleanings will be assessed on lab and pilot scales. The organic and inorganic natures of the irreversible fouling formed during long-term filtrations (and repeated cleanings) will be characterised in detail, allowing recommendations for sustainable operation and performance.