Desalination an expensive option
Jackie Cumming, of Waikanae Beach, asked:
We’re increasingly worried about not having enough fresh water. But we’re surrounded by salt water, which is desalinated in emergencies. What are the prospects for largescale permanent desalination plants that could help solve our freshwater shortages?
Simon McDouall, of the 2nd Engineering Regiment of the New Zealand Army which runs the defence forces’ desalination plants during emergencies in New Zealand and overseas, responded:
The prospects for largescale permanent desalination plants solving growing freshwater shortages are promising. Several countries already use such plants. Israel, for example, gets around 40% of its domestic water from desalination, while Saudi Arabia, United Arab Emirates, and Kuwait all rely heavily on desalination as a source of clean water.
California is currently experiencing its worst drought in over a century and has also begun investing heavily in desalination plants.
The biggest problem with largescale desalination is the cost. Both the building of a plant and the continuous production of desalinated water is hugely expensive.
The Carlsbad desalination plant in California cost $US1 billion to build and is expected to cost a further $60 million a year to operate. This will only provide enough clean water for around 7% of San Diego’s requirements.
Companies and countries are trying to lower the cost of desalinating water by using cleaner energy sources.
Saudi Arabia, for example, is currently building a desalination plant that will be, at least partially, powered by solar electricity.
Another major issue of largescale desalination is the environmental damage the process can cause. As these desalination plants take in salt water straight from the ocean, fish and other small sea life can be killed or harmed in the waterdrawing process. Further to this, only around half the water that is drawn becomes drinkable, the other half contains the concentrated salt and if dumped carelessly back in the ocean can kill marine life.
So, while largescale desalination may be a partial solution to a lack of fresh water, it’s current costs are so high that it would not be practical to expect it to solve the problem completely.
In the future, however, as improvements in technology and renewable energy continue and enable the cheaper production of water with minimal environmental damage, it may become a more viable, affordable solution.
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