| Archive for Downsizer For an ethical approach to consumption |
| James |
UK's first de-salination plantFrom ENDS (free subscription environmental journal)Thames Water opens £270m desalination plant 3 June 2010, 12:07 The UK's first mainland desalination plant was officially opened on Wednesday 2 June by the Duke of Edinburgh. The Gateway facility was built by Thames Water and is sited at Beckton, east London. The plant can treat 150 million litres of water a day, enough to supply a million people or a sixth of London’s population. It will be used only in times of drought. The Environment Agency classes the capital as "seriously water stressed" and believes the demand for water could outstrip supply in hot dry weather. The plant boosts the company’s available resources but has been controversial. It was opposed by former mayor Ken Livingstone because of its high energy use (ENDS Report 376, May 2006). Thames appealed successfully, pledging the 14-megawatt plant would run on 'green' energy supplied by on-site biodiesel generators (ENDS Report, June 2007). The plant takes water from the Thames estuary at low tide to obtain the least salty water, clarifies it through coagulation, filtration and membrane ultrafiltration before pumping it through a four-stage reverse osmosis membrane process. The finished water is remineralised with the addition of lime and disinfected by chloramination before being pumped along a 14-kilometer pipeline to the company’s London distribution system at Walthamstow. Thames estimates the plant uses three times as much energy to produce a litre of water as a typical water treatment process. The site is located next to the company’s mammoth Beckton sewage treatment works which serves most of central and east London, and Thames even considered drawing its effluent directly into the desalination plant. This would have been technically easier and more energy efficient, technical staff told ENDS. It was ruled out mainly due to fears that the public would object to sewage effluent being converted directly back into drinking water. 
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| jema |
When will people realise that biodiesel is not clean energy 
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| Pilsbury |
But the report does not claim its clean energy, just 'green'. And from the amount of chip shops and takeaways we have here (2 miles from the plant.) it wont be hard to get the used oil. | ||||||
| sean |
Damn, I was going to quibble about the Channel Islands, but they sneaked the word 'mainland' in. | ||||||
| T.G |
ok - now this is where I demonstrate my oodles of empty brain cells.... but don't you remove salt primarily from water via some heat process?... and if that’s so why then can't they use solar energy as a means to desalinate salty water ? | ||||||
| sean |
If you want the salt you remove the water by evaporation. They want the water though, hence the reverse osmosis and so on. Think of them as having built a giant kidney. | ||||||
| Brownbear |
So Londoners are going to be drinking hi-tech artificial urine? |
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| robkb |
No change there, then... Cheers, Rob. |
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| T.G |
yes but then can't you collect the evaporated water? and unevaporate it (what’s the blinking word) - sorry my word smithery (made up I know) is at a loss today - new tablets 
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| Pilsbury |
yes and up to now its been called lager and costs £3.50 a pint, at least this stuff will be cheaper..... ps becton sewage plant had some of the best tomato plants I had ever seen, loaded with fruits and huge at one time, aparently the human gut lets the seeds pass through and then the water and fertalizer available makes them grow well, question is would you eat one?? |
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| Behemoth |
Condensation. |
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| T.G |
Aha! condensation indeed that was the word i was thinking of
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| zigs |
Some alternative ways of getting water :
http://www.ecofriend.org/entry/10-interesting-ways-to-harvest-water-from-air/ |
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| James |
The other way of doing it, as The Grange suggest, is by distillation: add heat (sometimes from the sun) to vaporise the water, then re-condense it against a cold surface. I believe Saudi Arabia has some Solar powered distillation de-sal plants. But they have lots of solar energy and a small population whereas London has a huge population, and not much sun.
The volumes of water they're talking about in the article are massive- it would fill a tank one hundred metres long and one hundred meters wide and as deep as a three story house. To produce that much water per day would take a truly mammoth solar powered plant, probably not very realistic in the south east of England. I doubt solar is a viable option, and I don't like the idea of using bio-fuel. The only real option in my opinion is to greatly reduce the amount of water we use. London has the same rainfall as Istanbul, and half that of Sydney. Rather than trying to exist as a city in a wet climate, it needs to start thinking like a city in a dry climate. This plant will produce 16 % of London's water supply. Reducing personal consumption from 150 litres per day to 125 litres per day would provide about the same volume. |
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| vegplot |
We could flog them a few buckets full. | ||||||
| toggle |
reducing leaks would have more effect |
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| Bebo |
Why not make more use of artesian wells. I was under the impression from something I read a few years ago that due to the reduction in heavy industry in London since the 50's that extraction had reduced dramatically and as a result the water table was rising. They'd had to start pumping out tube lines that had been dry for years and the risks associated with digging deep basements in central London developments was rising. | ||||||
| James |
The water under London is shockingly polluted- much less palatable or easy to treat than water from the river Thames.
Also, in general the amount of water you can get out of the ground is much less than out of a big river. |
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| Behemoth |
Thames have a lot to do in terms of controlling leakage but it’s not the whole story. The region is reliant on river and borehole extraction. If the levels of these fall due to a drought Thames will not be able to abstract water from them, there’ll be no water to go into their leaky pipes. They’ve only got one reservoir so have no where to store water and were prevented from building one a while back. The desalination plant provides a water source and treatment capacity when it’s needed. |
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| James |
also, the leakage from the system is factored in when the the water companies calculate how much water they can abstract from the boreholes. The Environment Agency's Thames chalk numeric model uses leakage as one of of its inputs for groundwater recharge- this water isnt lost, it just goes into a different "pot". |