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  • In 2015 a series of

  • droughts started to dry up this dam,

  • the source of almost half of the water available to Cape Town, South Africa.

  • In this satellite time-lapse

  • you can literally see the stored water

  • decrease month by month.

  • In 2018 the city was approaching "day zero".

  • Shorthand for the day the taps run dry

  • and people would have to queue to get water rations.

  • Cape Town was the first major city to risk running out of water,

  • but it's not going to be the last.

  • JakartaLondon, BeijingTokyo

  • could all face their own day zero in the coming decades.

  • Most parts of the world at least for a month a year

  • are experiencing some water stress or water scarecity."

  • The gap between demand and supply of water is narrowing down.”

  • Our planet is awash with water.

  • More than one billion trillion liters to be precise.

  • The problem is that 97% of Earth's water is salty

  • and most of the freshwater is frozen in ice caps.

  • Less than 1% of the Earth's water is drinkable.

  • That makes one solution especially promising:

  • Desalination seems a pretty straight forward solution:

  • you take that undrinkable salt water, you remover the salt,

  • and you have an unlimited supply of freshwater.

  • So, why are we not building more desalination plants?

  • Desalination is a natural process that's been known for millennia.

  • As already Aristotle noted, the sun dissolves ocean water into vapor

  • which then condenses again and falls back as rain.

  • His compatriots took note.

  • Greek sailors boiled seawater for long trips.

  • Romans used clay filters to trap salt.

  • These are still the two basic principles used today.

  • Thermal desalination uses heat.

  • Salt's boiling point is a lot higher than water,

  • so if you boil salt water,

  • only freshwater will evaporate, leaving all the salt behind.

  • Membrane desalination uses pressure.

  • Saltwater, here colored in red for clarity,

  • is pressed through a membrane that is only partially permeable.

  • Freshwater can pass through,

  • here colored in blue, but the salt is trapped on the other side.

  • The technology didn't improve much until the 19th century,

  • when industrialization and population growth encouraged more research.

  • Population growth is the main driver for increasing water scarcity.”

  • Manzoor Qadir is an environmental scientist

  • with over 30 yearsexperience in water management.

  • Say, for instancethe Middle East and North Africa region.

  • That region has a population of about five percent of the world's population,

  • but just has one percent of the global water resources.“

  • And soon, another factor could make desalination even more crucial:

  • As the climate warms more water will evaporate.

  • And as Aristotle noticed,

  • more vapor equals more clouds, equals more rain.

  • But that rain won't fall evenly.

  • This map shows how precipitation will change as the climate warms.

  • Regions in purple will get more rain, those in orange less.

  • Now compare it with this other map.

  • The red dots here show areas that already today don't get enough water.

  • Dry areas like California and the Middle East will see even less rainfall.

  • Other countries like India will have more rain in the monsoon season,

  • but less in the dry season, when people need it most.

  • This will make desalination even more popular.

  • "And that has really started to explode, let's say since the late '80s and '90s.

  • But especially in the last 20 years, you've seen a big acceleration."

  • Edward Jones is a Ph.D. researcher

  • who has put together a "state-of-the-art outlook on the status of desalination."

  • "Nowadays we have around 16.000 desalination plants

  • which are producing more or less 100 million m3 per day.“

  • But take a closer look at this map.

  • "If you look at how much desalinated water we produce on this globe,

  • currently,  71% is produced in high-income countries.“

  • That's because desalination is very costly.

  • Boiling billions of liters of water takes a lot of energy.

  • In the Middle Eastthe availability of oil and especially fossil fuels makes the thermal processes

  • cheaper, but for other types it can be 25 or 30 times more expensive.”

  • But that energy doesn't have to come from fossil fuels.

  • A startup in Berlin has a sustainable alternative.

  • My name is Ali Al-Hakim,

  • I am the co-founder and CEO

  • of the company Boreal Light.

  • I moved from West Germany to Berlin... Let me just drink a glass of water.

  • Do you also want to drink something?“

  • Your water?“

  • If you like.“

  • Yes, please!“

  • So the water comes from the borehole tank to the system.

  • And after thatit's going through the buster pump.

  • With 40 bars of the water is pressured to the membranes.

  • It's clean, desalinated water, with green energy.“

  • Green energy: that's the key to the company's success.

  • You are looking at of their plants in Kenia.

  • These solar panels keep the cost of water low

  • in villages like this, where electricity is not available.

  • We get the water for free, we get the electricity from solar and wind for free,

  • so we can now produce one thousand liters for fifty cents.

  • This price is actually competitive [with] clean water from rivers or from boreholes.“

  • But there's another problem.

  • What do you do with this water?

  • We forced all of this salt out of the water to produce our freshwater.

  • But now the salt is still contained within our substance,

  • but it's just in a smaller volume, so it's more salty.”

  • This water is called brine.

  • At the global levelwe produce more brine than we produce desalinated water.“

  • You've got your pipe that's coming out of the desal[ination] plant.

  • You're discharging hypersaline water here,

  • and as it flows out it will sink because it's more dense.“

  • The salinity and the temperature can also deplete the oxygen available

  • and this is what's causing the organisms more damage,

  • just the lack of oxygen. They are basically suffocating.“

  • Brine can also contain chemicals harmful to sea life.

  • There needs to be a better plan for the industry of dealing with this brine.

  • We are producing more waste with no plan.“

  • But what if this waste could become a resource?

  • Tomatoes, seaweedand certain fish can tolerate high salinity.

  • Boreal lights uses brine to cultivate them in tubs like this.

  • "There's also the opportunity for salt recovery and for metal recovery."

  • "At the moment technologies are available for brine management,

  • but those are on a very small scale.

  • The challenge is how we can transform those small-scale technologies

  • intolarge-scale operation.“

  • Desalination is not a magic formula.

  • The process must become more efficient before low-income countries can afford it.

  • Plants must convert from fossil fuels to renewable energies to limit emissions.

  • And the whole industry needs to come up  with a plan to deal with this brine.

  • But plants like this are already a lifeline for many communities.

  • It's very important to realize that desalination is here to stay.

  • We really need to work towards solving the challenges of desalination.“

  • This is a gradual process this will not happen overnight.

  • But I can see that there is a push

  • there is a willingness to harness the potential of desalinated water.“

  • Today Cape Town is doing

  • a lot better and the dam is almost full.

  • The city was rushing to build desalination plants to avoid day zero.

  • But the solution was not desalination or any other technology.

  • Citizens became water-wise.

  • They radically changed their water use,

  • and valued water for the essential and irreplaceable substance that it is.

  • Fun fact: The amount of desalinated water we produce every year

  • is comparable to half the water that falls off the Niagara Falls every year.

  • That's it from us. As you can guess from this quick time-lapse,

  • these videos take a lot of time. If you liked it, please give it some love.

  • Share, subscribe, press the like button.

  • And stay tuned. We have more videos like this coming out every Friday.

In 2015 a series of

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Can desalination solve the global water crisis?

  • 12 1
    joey joey に公開 2021 年 06 月 08 日
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