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Water, water everywhere...

Posted 17/09/2013 by sevans

…but not a drop to drink – so go the lines in the Rime of the Ancient Mariner by Samuel Taylor Coleridge. But the truth is not so very different, as freshwater supplies are becoming scarcer by the day due to the demand of agriculture and industry, apart for the growing global populations need for drinking water. And the problem is not just limited to the developing world, Western countries are also starting to see their water supplies squeezed.

Just as with energy and food, securing water supplies is becoming a major challenge for countries and regions around the world. One approach is to turn undrinkable water, such as brackish or seawater, into potable water using desalination, but this has been seen as an extremely expensive route that only suits those countries where freshwater is almost non-existent, such as in the Middle East. Today, however, there are around 13,000 desalination plants in operation or under construction in 150 countries, and the UK opened its first municipal plant in Beckton, east London, in June 2010. By 2050, the UK Institution of Chemical Engineers (IChemE) predicts the number of plants worldwide will have double with a further 18,000 plants coming on-stream, including at least a further four UK municipal facilities and up to 800 smaller units.

But conventional thermal desalination plants are energy intensive, utilising evaporative and condensation processes, while membrane systems, using reverse osmosis, for example, require high pressure pumps to force the water through the membrane; the energy needed for reverse osmosis being proportional to the salinity of the starting material.

However, according to the IChemE, changes in technology, combined with population growth and unpredictable weather conditions exacerbated by climate change, are likely to make desalination more viable in the UK. ‘While improvements are continuously being made to RO membranes making desalination more chemical and energy efficient, some of the most exciting developments in desalination are with breakthrough technologies,’ says Martin Currie, an independent water consultant and member of the IChemE’s water special interest group. 

‘Researchers are currently working to scale-up biomimetic membrane processes employing aquaporin proteins – found in our kidneys – that let water through much more efficiently than conventional membranes,’ he says. ‘Also UK universities and companies are at the forefront of forward osmosis (FO) – a technology now in commercial operation that uses osmosis to suck water through the membrane rather than just pumps to push it. Both technologies promise huge energy savings and FO plants are already seeing massive reductions in the amounts of chemicals required to maintain the membranes.’

So desalination is becoming a practical solution even in the UK – no longer will there be cause for apocryphal stories like the water that we drink having already passed through many bodies before reaching us. Or will there?

Of course, with limited resources water is just one of many recycled substances that we currently, and will increasingly have to use, so why should we be squeamish about the water we drink, even the seawater has been recycled many, many times?

Neil Eisberg - Editor

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  • Anonymous said:
    15/10/2013 06:40

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  • Anonymous said:
    14/10/2013 07:14

    Although I'm not a community<a href="http://zkqhpu.com"> meebmr</a>, I've been researching the impending desal in Cambria for about 6 months now, just because it sparks my interest. There are a couple of problems with your argument against desal. First, recycled water isn't potable and therefore wouldn't be the best option for Cambria. The other leading water supply source in California is importing water. Both importing water and recycling water do require less energy and output less emissions that desal but the needs of Cambria can't be met with either option. California currently has the largest imported water infrustructure in the world. The problem is, imported water has to be just that, imported. California has been in a drought emergency for 3 years now. With drought seasons getting more severe as the climate changes, expanding the imported water system would not be logical. Therefore, the remaining option is desal. Secondly, a desal plant is considered hazard mitigation for Cambria. Currently, Cambria does not have enough water and pressure for adaquate fire flow. That means that if a fire were to occur (Cambria is located in a very high fire hazard zone, fyi) there would not be enough water to adaquately fight it. Seeing as how most of the Montery Pine trees in the area are diseased and dying, it would be difficult to contain the fire. A lot of houses in Cambria are located within these pine trees. Second, the price of desal is higher, that's true. So far though, the State has provided Cambria was approx. 10 million. Yes, some of the money (about 1/4) will have to come from residents. Is that all that bad when you consider the surcharges currently in place? These surcharges are subject to increases, which the residents have already seen. Third, desal does not destroy the environment! This is perhaps the arguement that irks me the most. Desal changes the environment, it doesn't destroy it. Changes would include decreasing the pressure put on local streams. This would allow the environment to return to it natural state, increasing the fish population to it's normal numbers, etc. Right now, drawing water from the natural aquifers are negatively impacting the environment, desal would reverse that. As for the water intakes, with current technology, these don't impact the environment. I can't remember where I saw the particular picture I'm thinking of but it showed organisms attached to the water intakes. They were living on the intakes. Desal also puts out water with higher concentrations of salt. This doesn't destroy the environment, it changes it. The area it changes isn't that large either. Think of Diablo Canyon, it outputs warm water. The waters surrouding Diablo Canyon are home to one of the largest populations of seals (I may have the animal species wrong, this is off of the top of my head). Basically, colder water organisms moved out and warmer water organisms move in . There's just as much life there as before. Desal would have a similar effect in terms of salt concentration, not temperature. Fourth, the desal plant would produce enough water to manage Cambria at its current population. Even if it DID allow for a little growth, it's worth it. More homes could be saved in case of a fire! So maybe you're still asking how you'll benefit from desal. I'll review: Adaquate fire flow=saves homes, saves lives, saves money in case of a disaster. Environmental benefits= relieve pressure on streams. In addition, maybe a controlled burn could be done to revive the pine trees that Cambrians love so much. Residential benefits= clean water! and no more rediculous surcharges. I understand that this is the perspective of an outsider and therefore the desal plant doesn't affect me. However, I have done my homework (literally) on desal in general and how Cambria would benefit from this type of water supply. Conservation is always #1 but it is unrealistic to think that conservation on its own will solve Cambria's problems.

  • Anonymous said:
    13/10/2013 02:09

    Your information is prneeetsd concisely and I especially like the graphic that further supports the topic. It will be young scientist citizens like you that will care enough about an issue like this to want to make a difference. Keep thinking about what you can do now and what you can do when you grow up' to make this difference!