# Can we change sea water to drinking water cost-effectively?

Discussion in 'Science & Society' started by Saint, Jun 29, 2015.

1. ### SaintValued Senior Member

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Can we change sea water to drinking water effectively? With low cost?
Our technology can't do that?

3. ### billvonValued Senior Member

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Relatively low, yes. The general ways of doing it are:
Reverse osmosis. Pump salt water against a membrane.
Evaporation distillation. Big solar farms that evaporate and condense water at lower temperatures.
Vapor distillation. Fairly efficient method to boil water at much lower temperatures and pressures than we usually use.

5. ### Fraggle RockerStaff Member

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A "solar still" was invented several years ago that can distill water that is actually dirty, not just salty. It uses the heat differential of a sunny day to evaporate the water and collect it in a separate, clean container. It can process one liter of runoff per day. It's a small plastic device that can be mass-produced for about five dollars. A multi-billionaire philanthropist like Bill Gates could send one to every citizen of the Third World--where there's enough sunshine (and enough waste water) to support the population.

7. ### exchemistValued Senior Member

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The city of Dubai has used waste heat from the thermal power station at Jebel Ali to do this for over 30 years, via distillation.

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In Australia we have a number of Desalinisation plants. Most were set up during our last El-Nino event which lasted quite a few years.
In that period the main dam supplying Sydney's water was around 40% full from memory.

https://en.wikipedia.org/wiki/List_of_desalination_plants_in_Australia

9. ### billvonValued Senior Member

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Fortunately someone is working on something very similar with that goal in mind:
https://en.wikipedia.org/wiki/Slingshot_(water_vapor_distillation_system)

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10. ### brucepValued Senior Member

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So a consequence of the El Niño is drought in Australia? In Southern California it's mid 70's water temperatures for surfing and salt water fishing in the summer and huge winter storms and mudslides in the winter. The drought is so bad I was hoping for the El Niño. Who knows what going to happen with the drought. My fear is that it's going to wind up Borrego desert meets the Pacific Ocean.

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Yep, the last one lasted more than a decade, and although we have had plenty of rail since, the BoM is now telling us we are entering a new El-Nino phase.
It's no stretch of the imagination to say that we have some 10 to 12 year old children in the bush/outback that had never seen rain.
[BoM = Bureau of Meteorology]

12. ### SaintValued Senior Member

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But most countries still depend on rain water.

13. ### spidergoatVenued Serial MembershipValued Senior Member

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About a quarter of all Israel's water needs are from desalination plants.

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14. ### AlexGLike nailing Jello to a treeValued Senior Member

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The largest desalination plant in the world is in Israel. The Saudis are building a still larger one. The plant on the island of Aruba used to be the largest in the world and supplies all of the island's drinking water.

15. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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Rain water is free.

16. ### psikeyhackrLive Long and SufferValued Senior Member

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Got a link for that Fraggle?

There is probably a question of quantity of water also. How big is the device? How big a piece of land does it take per quantity of water?

How many poor people don't have any land? Aren't the economic power games designed to keep people poor?

psik

17. ### iceauraValued Senior Member

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Clean rain water available in the dry season in adequate quantity is not free.

18. ### brucepValued Senior Member

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My hope would be that the group catches on pretty soon. In Southern Cal it's looking as though this might wind up Borrego by the sea. We should have preparing for this long ago. Oh that would mean folks would have to recognize there's a problem.

19. ### danshawenValued Senior Member

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3,950
http://www.mcclatchydc.com/news/nation-world/national/article24765472.html
(Israel no longer worried about its water supply, thanks to desalination plants)

https://en.wikipedia.org/wiki/Desalination

"Israel Desalination Enterprises' Sorek Desalination Plant in Palmachim provides up to 26,000 m³ of potable water per hour (2.300 m³ p.a.). At full capacity, it is the largest desalination plant of its kind in the world."

According to the table included, the largest such facility (Sorek) opened in 2013 and produces about 228 million cubic meters of water per year at a cost just over US $1.00 / cubic meter. 20. ### BellsStaff Member Messages: 22,718 Some parts of Australia have been in severe drought for several years. Even with heavy rains from the El Niña event of recent years, that affected many parts of Queensland, there was still drought in many places. Some areas like Longreach in outback Queensland are nearly running dry. We got through the last severe drought without desalination plants. To put it into some perspective, 80% of my home state is currently drought declared. We are currently going into another El Niño event. Which means more severe weather events for the East Coast and more drought affected areas getting even less rain. I think one of the most bizarre things with California is the way in which it took so long to respond to the drought. In Australia, we know and understand droughts and we know that water is not a finite resource. So at the hint of a drought, stronger water restrictions are put in place, our use of water is limited. We don't water our lawns or gardens. We are given incentives and encouraged to get water tanks. We are charged more if we use too much or over our allotted amounts. These amounts are reduced when droughts are on the horizon. We are educated about being water wise, reusing clean waste water (not sewage obviously) for gardening purposes, etc. Things like mandatory dual flush toilets and water saving shower heads and taps.. This is a way of life for us, whether there is a drought or not. I don't even think we can buy a non-dual flush toilet here anymore, and the same goes with taps and shower heads. We are encouraged to plant natives which are drought tolerant, our lawns turn brown, then they turn brown. It is a rare sight here to see anyone water their lawns or nature strips. In times of drought, if you are caught watering your lawn, you can be fined. Usually what many councils do when there is a drought on the horizon is to restrict using the hose on alternate days depending on the house number you have. And then if they notice the water levels going down too much, that is banned. And even with the hose restrictions of every second day, people don't water their lawns. Stuff like this: As California’s severe drought deepens and officials look to reduce water consumption in every possible way, the state appears to be sending mixed signals as to which water-related activity is the most egregious. The entirety of California is currently experiencing drought conditions and more than 80 percent of the state is classified as an extreme drought. Laura Whitney and her husband, Michael Korte, have been trying to conserve water in their Glendora, California home by cutting back on lawn watering, taking shorter showers, and doing larger loads of laundry. Now, they are facing a fine of up to$500 for not keeping their lawn green.

Doesn't happen here.

In an extreme drought like California is facing, it should be a crime to water the garden and lawn. It is here during extreme drought events. If you have a water tank or have access to bore water, sure, otherwise, no. And even then, we don't water our lawn.

I think California's drought and dwindling water supplies were and are made worse by an absolute disregard for the conservation of water and a too late response to what was clearly an emergency issue 4 years ago.

An El Niño event might bring some much needed relief to the State, but until the State becomes more waterwise all the time, it won't be enough and will never be enough.

21. ### brucepValued Senior Member

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Don't believe everything you read. My guess would be I'm using much less water than you. I'm recovering about 20 gallons of 'rain water'/day from 3 Idylis portable 12,000 btu air conditioners. Flushes all the toilets with the rest getting dumped on my lawn. Like I said don't believe everything you read. Since you really don't know what's going on here you should probably withhold your judgement until you do.

22. ### river

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Why not distilled salt water? Just saying.

23. ### BellsStaff Member

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Why are you dumping it on your lawn?

I live in a drought affected state, much longer than the 4 years that California has been drought affected. Pretty sure our water saving measures far outweigh your State's water saving measures, considering that local councils in your home State are still fining people for not watering their lawn and their garden.

There is no need to get so defensive about your State's continued failure to manage it's water resources. I think failing to acknowledge this properly and not putting pressure on the State to fix its problems is not going to help everyone in the long run.

Because you could have a rain event, but unless they learn to manage water more effectively and put measures in place to reduce water use State wide, then it will keep happening each time there is a drought. And there will be more.

And since you clearly do not know or understand just how bad it can get unless your Government pulls its head out and does something, then you really should not be passing judgement on me as you have done.

If you are saving 20 gallons of water a day from running your portable airconditioners every day and from rain and what I assume are your water tanks outside and connected to your downpipes, then great. Just be mindful that portable airconditioners are not that efficient and the use of water to generate electricity tends to be quite high, so whatever you are saving, may cost more in general in the long run. Instead of watering your lawn, you should look to using it to wash your clothes, for example. And then use that waste water from the washing machine to water your lawn and flush your toilets.

I would also recommend changing toilets and all taps and shower heads to water saving ones, like dual flush toilets and water saving taps and showers. And recycling water from showers and the kitchen to use in the garden or to flush your toilets as well.

This was all flagged back in 2010 and water saving messages only started to be pushed out by the Government in what? 2014?

So Queensland gave them goals. Specifically, it asked that residents use just 35 to 40 gallons of water per person per day -- a savings that could be more easily attained if residents reduced their seven-minute showers to four minutes. In addition to giving residents free shower timers, that message was widely advertised on televison and in outdoor advertising. Those who significantly exceeded the goal were sent letters asking them to explain their water use; of those, 34% reduced their consumption to the appropriate level immediately and 9% discovered they had a leak.

In addition to outreach, Queensland was aided by a \$261-million rebate program that provided its residents with 508,000 water-saving devices, including rainwater tanks, low-flush toilets and water-efficient shower heads. The result was a population that didn’t just meet the stated goal but exceeded it.

Although rain has since returned to Queensland, and water use levels are now less restricted, Spiller said, "one of our objectives is that residents use only what they need."

By Queensland standards, that’s about 30 gallons per person per day, compared with 200 to 300 gallons per person per day in Southern California, said Peter Beattie, commissioner to the Americas of the Queensland state government.

You save 20 gallons a day to flush your toilet and water your garden? We use 30-40 gallons per day in all of our water use and recycle that for use in the garden.