In the debates about dwindling natural resources, water is often left out of the picture. Perhaps unsurprisingly, we take water for granted – it’s everywhere we look: as rain, the mains supply, reservoirs and oceans… the supply seems endless.
The key word here is ‘seems’. Water is a precious resource, fundamental to all life on Earth, and yet not much is said about our limited supply. It’s not just dripping taps either: water is used to make the food we eat and the clothes we wear. All of us leave behind a ‘water footprint’, and a pretty big one at that.
It’s not all bad news though. The world is waking up to the problem, and innovative new technologies and strategies are being developed to create new sources of water and recycle old ones.
Perhaps the fastest growing of these is desalination. Although energy costs drive up the price, this popular technology creates safe drinking water from seawater. Arid, coastal countries such as Israel are investing large amounts of money in bigger and better desalination plants.
Some, if not most, desalination plants use a technique known as ‘reverse osmosis’ (RO). In normal osmosis, water will move across a semi-permeable membrane (one that will allow water, but not salts, through) from a solution with a low salt concentration to one with a high salt concentration until the concentrations even out. But, if enough pressure is applied to the high concentration solution, the water can be forced back across the membrane, producing more water with a low salt concentration – the desalinated water.
However, solving the problem isn’t just about accessing new sources of water. The keyword, as with regards to all environmental matters, is sustainability. Yes, the oceans are pretty huge, so we’re not likely to run out of water from there any time soon: but is this really what we want to aim for? In order to waste as little water as possible, we need to reuse our wastewater. And yes, that does include sewage.
Reclaimed water, as it’s known, has a lot of applications outside our drinking water system – irrigation and flushing toilets, to name two – so it’s certainly not about drinking recycled sewage. Plus, it’s not just sewage water (or ‘blackwater’) that we waste: used bathwater, washing machine water and dishwashing water (‘greywater’) can all be reused, but the infrastructure just isn’t there in most countries.
The technology’s there though, and has been for a while. On the International Space Station for example, there’s a working system to recycle wastewater called ECLSS that has been used since May 2009. Also, in Tel Aviv 100% of wastewater is treated, and the reclaimed water used for agricultural and public water.
Sewage reclamation plants use three stages. First, the solids in the wastewater are filtered out through a series of physical barriers. Secondly, the water enters reactors filled with bacteria, which consume the organic material in the water. Finally, the water is purified by forcing it at great pressure through sand and it is then pumped out of the plant, safe and ready for agricultural use.
These are just two of the ways that water waste can be reduced, or even eliminated. There are also some crazier schemes (such as the Red-Dead canal, a project proposed to pump water from the Red Sea across to the dwindling Dead Sea) and some exciting new technologies (like ultraviolet water treatment) around.
It’s definitely worth keeping an eye on your water waste, too, because with supplies dwindling and water metering gaining popularity, it’ll soon be a closer problem than you think.
For more information, visit www.waterfootprint.org.