Is Seawater Desalination ‘Green'?29/03/2010 |
|
| An article published in the Journal of Water Supply: Research and Technology discusses a general ‘best available technique' (BAT) approach for seawater desalination plants. The authors describe the resource consumption and environmental impact of various methods. |
|
It is unanimously agreed that energy, water, climate change and the world water crisis are inseparable global problems. Energy is needed to deliver water, and water is needed to generate energy. Energy use furthermore brings about climate change, which may intensify droughts and water crises in some parts of the planet. Australia, for instance, is currently experiencing the harshest drought in its history and has turned to desalination in order to alleviate problems of water scarcity in the major cities.
It is agreed that seawater desalination capacities will continue to grow rapidly in the coming years. However, due to the use of chemicals which are discharged into the sea along with concentrate, marine protection groups have been voicing their concerns. In addition, seawater reverse osmosis (SWRO) plants are also criticised for their extensive use of energy and greenhouse gas emissions. The authors quote a review in Nature which described desalination as "chemically, energetically and operationally expensive". Despite these costs and environmental concerns, many headlines have been appearing describing desalination as "green" and "sustainable".
The authors argue that, as desalination capacities continue to grow, an objective understanding of the real environmental stakes is necessary. They state that an environmental impact assessment (EIA) and a reference document describing ‘best available technologies' (BAT) are required. Although an EIA manual was published in 2008, the equivalent in BAT does not yet exist. The article, therefore, describes a first general BAT approach for SWRO.
The SWRO process is analysed by the authors with regard to the main sub-systems (i.e. intake, pretreatment, desalination process, cleaning and concentrate disposal system). For each sub-system, comparable processes and methods of operation are compared in order to identify BAT. Different environmental criteria such as water and energy use, the use of chemicals or other materials as well as resulting emissions and their likely environmental impacts are all taken in account.
The figures provided by the authors - one for each of the five processes listed above - describe the positive and negative features of each aspect in terms of technical and environmental considerations. These figures allow the reader to see that if technical, economical and site-specific environmental limitations could be neglected and environmental benefits prioritised, the most preferred design would be a SWRO plant receiving water from a subsurface intake and discharging the concentrate by an enhanced multi-port diffuser system in a suitable oceanic site. An acceptable alternative where a subsurface intake is not possible is an offshore submerged intake fitted with a passive screen (large surface area with low flow velocities) and fine-mesh screens which can be backwashed with air.
The authors conclude the article by describing seawater desalination as the "epitome" of the global energy and water crisis. By establishing a BAT reference for desalination and acknowledging that water and environment are valuable commodities, however, the industry can commit to "green" practices.
Read more about: energy scarcity Reverse osmosis environment drought climate desalination Source: Sabine Lattemann, Maria D. Kennedy and Gary Amy, 2010. Seawater desalination - a green technology? Journal of Water Supply: Resea Website: http://www.iwapublishing.com Supplier: International Water Association (IWA) More news from this supplier: World Water Professionals to Meet Efficient 2011 Conference Regional 2010 IWA Project Innovation Awards Winners IWA World Water Exhibition Developing Water and Climate Change Journal Prepare Cities for Climate Change Agencies Rush Water to Haiti Call for Abstracts Water Research Conference Help Protect Water Resources Widespread Consensus on Pressing Issues NASA Mission Takes Stock of Earth's Melting Land Ice Alleviating Water Problems In Abu Dhabi Dutch Experts to Design Flood Safety System 2.8 Million Gallons of Water Saved In Seven Months Oil and Gas Water Reuse Pilot in Alberta UN Agency Funds Irrigation Improvement Projects Smart Grids Crucial for Future Utility Operations UK: Underinvestment in Flood Infrastructure Nearly 10 Million to Clean Up US Beaches California Clean Water Agencies Champion Clean Energy Initiative 
Comments (0): |
© 2012 Geomares Publishing Copyright reserved. 