Water Journal : Water Journal February 2014
FEBRUARY 2014 WATER 31 Workshop Report yet commercialised -- for example, forward osmosis membrane distillation -- to develop and demonstrate energy-ef cient desalination at small scale. About four to ve pilot plants are to be built at Abu Dhabi and the plants operated on a continuous basis for at least 18 months to demonstrate reliable performance of the technologies. Phase 2 (after 2016) involves implementation of the developed energy-ef cient desalination technology in large-scale, fully renewable energy-powered seawater desalination plants. Third party proponents of suitable technologies must commit as 50-50 partners with the government to the use of their technology in the attempt to achieve commercial scale. Importantly, the IP remains with the proponents. The aim of the exercise is R&D transformation, together with demonstrable sustainable energy use, as well as preserving the environment for the bene t of humanity. On Day 2, Ms Miriam Balaban, representing the European Desalination Association, chaired a session featuring Professor Emeritus Jan Schippers from UNESCO-IHE, Institute for Water Education in Delft, who gave a presentation focused on particulate fouling. He discussed the reliability and predictability of the silt density index (SDI). Doubts have arisen about SDI tests used in predicting the fouling of RO and NF membranes, variable results with temperature and membrane manufacturers and correlation with fouling of RO and NF membranes in full-scale plants. The MFI (modi ed fouling index) proposed to overcome these de ciencies of the SDI test. Theoretical calculations and measurements with membranes having smaller pores than 0.45mm are responsible for fouling RO and NF membranes, hence the justi cation to develop MFI-UF measured at constant ux. The MFI-UF enables prediction of the rate of fouling of RO/NF membrane. Achieving water recovery from RO treatment of brackish inland waters, especially in northwest Western Australia, commonly results in yields as low as 50% with high volumes of brine and troublesome scale precursor chemicals such as silica. Dr Peter Sanciolo, one of a number of NCEDA grant recipients who reported their research, has concentrated on dealing with the silica as a rst step to increased water recovery. The work involved using commercially available alumina adsorbent under varying temperature, pH and ux to remove the scale precursors. He is continuing to examine phenomena arising during regeneration of the adsorbent to improve its reuse and contain costs. Dr Bea Sommers, Research Fellow at Edith Cowan University in Perth, also spoke about the management of brine discharge following RO treatment of brackish waters in inland locations. Site conditions, the properties of the brine, and whether or not further treatment was possible to reduce brine volume and/or improve water quality constrain opportunities for bene cial uses. Ecosystem services refers to the bene ts that people get from nature, gratis. They are usually grouped into four categories: provisioning (food, sh); ood control; recreation; and soil formation. Pricing these services is not always possible, although it will be important, as addressing the future management of brine has become one of the most challenging and costly dilemmas when permitting is sought for inland plants. In Australia, evaporation ponds are intended to be temporary storages prior to nal disposal, although requirements differ with the jurisdiction. Existing options -- deep well or aquifer injection, natural wetlands and streams if available -- are more familiar to most practitioners than the bene cial uses in the context of ecosystem services as advocated by Sommers. Staying with the solutions offered for brine disposal, membrane distillation crystallisers (MDC) can utilise brine waste heat energy; however, the problems in operating on a large scale involve overcoming the relative membrane ux, membrane fouling and scaling issues that can cause system failure due to membrane wetting. Professor Vicki Chen, Director of the UNESCO Centre at UNSW, looked at the effects of using transverse vibrational motion in a vacuum-enhanced submerged hollow bre membrane distillation system (VMD). Vibration enhancement increased membrane productivity, although not without the problems associated with membrane wetting. Professor Linda Zou from Adelaide University spoke on the development of graphene electrodes and application in brackish water desalination. Single-walled carbon nanotubes were combined with graphene oxide nanosheets in aqueous dispersion and then chemically reduced to form the carbon nanotube/graphene (CNT/G) composite as electrodes for capacitive deionisation (CDI). The structure of the CNT/G composite was highly porous, with single- walled carbon nanotubes (SWCNTs) sandwiched between graphene sheets that functioned as spacers and provided diffusion paths for smooth and rapid ion conduction. A portable prototype of a capacitive deionisation (CDI) unit has been operated for the rst time in Wilora, a community in a remote area in the Northern Territory, to remove salt from the brackish groundwater. The CDI unit has demonstrated suf cient salinity and hardness removal ability at the remote brackish water source, although a few issues still remain to be resolved. In a nal iteration, solar photovoltaic panels have been incorporated with the CDI unit on a trailer, which means that the operation of the CDI becomes totally self-sustained. The portable CDI unit proves to be a viable alternative solution to brackish water treatment, especially in communities in remote areas where building a reverse osmosis treatment plant is not practical, and it is expected we will see further applications of this technology. Another example of solar technology for humane purposes came with the presentation by Dr Trevor Pryor of Murdoch University. This research project originated from the needs of the remote Tjuntjunjarra community located 800km northeast of Kalgoorlie, where available water is scarce and highly saline. The existing supply source was troubled by high levels of nitrates. A series of project partners from industry, government, community service providers and research institutes combined to develop a suitable and sustainable desalination system, taking into account that any system had to be reliable and require infrequent maintenance, and produce a consistent volume of high-quality water (11,000--15,000 litres/day). A major focus of the project was overcoming the problem of intermittency of renewable energy resources by developing a cost- effective hybrid solar/waste thermal system to power an innovative thermal vacuum multi-effect membrane distillation desalination system. The facility has now commenced operations and so far appears to be meeting design criteria. CONCLUSION The Workshop was voted a major success by all attendees and served to provide an insight into the potential value of applied research, achievable at its best when research can be introduced to industry and community to meet their needs. More support for development and commercialisation is urgently required for the country to bene t from the best minds and the best science produced here in Australia.
Water Journal December 2013
Water Journal April 2014