Both Sydney and Melbourne are seriously considering building desalinization plants to augment their water supplies.

It's a simple process, really. The plants get seawater and boil it at a very low air pressure. The salt is removed in this process, and (relatively) clean water is produced that can then be filtered like rainwater and pumped into the water grid. The remaining salt can be dried out and sold (for table salt or to food manufacturers) or dumped back into the ocean.

Desal plants are not unsightly industrial monsters spewing out black smoke.

Of course, the process requires energy, so some environmental groups are a bit unhappy. Moreover, the excess salt that these plants produce, if returned to the sea, can cause higher-than-normal salinity in the area of the sea where they are dumped.

The best argument against them is the idea that we should recycle our wastewater and stormwater before we start on the seawater.

But, of course, what process can we use to recycle our wastewater? Removing sewage from water requires all sorts of filters and power as well. Ironically, the process behind a desal plant (boiling water at low pressure) can also be used to separate the water from the waste. Same process, but different byproduct.

Building desal plants will go a long way to ensuring future water supplies. However I think it is important that we do everything possible to reduce our wasteful usage of water at the same time.

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