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Growing up in northern Wisconsin,

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I've naturally developed a connection
to the Mississippi River.

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When I was little,

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my sister and I would have contests
to see who could spell

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"M-i-s-s-i-s-s-i-p-p-i" the fastest.

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When I was in elementary school,

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I got to learn about the early explorers
and their expeditions,

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Marquette and Joliet, and how they used
the Great Lakes and the Mississippi River

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and its tributaries
to discover the Midwest,

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and to map a trade route
to the Gulf of Mexico.

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In graduate school,

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I was fortunate to have
the Mississippi River

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outside my research laboratory window

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at the University of Minnesota.

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During that five-year period,
I got to know the Mississippi River.

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I got to know its temperamental nature

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and where it would flood
its banks at one moment,

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and then shortly thereafter,

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you would see its dry shorelines.

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Today, as a physical organic chemist,

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I'm committed to use my training

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to help protect rivers,
like the Mississippi,

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from excessive salt
that can come from human activity.

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Because, you know,

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salt is something that can contaminate
freshwater rivers.

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And freshwater rivers,
they have only salt levels of .05 percent.

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And at this level, it's safe to drink.

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But the majority of the water
on our planet is housed in our oceans,

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and ocean water has a salinity level
of more than three percent.

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And if you drank that,
you'd be sick very quick.

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So, if we are to compare
the relative volume of ocean water

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to that of the river water
that's on our planet,

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and let's say we are able
to put the ocean water

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into an Olympic-size swimming pool,

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then our planet's river water
would fit in a one-gallon jug.

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So you can see it's a precious resource.

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But do we treat it
like a precious resource?

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Or rather, do we treat it
like that old rug

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that you put in your front doorway
and wipe your feet off on it?

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Treating rivers like that old rug
has severe consequences.

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Let's take a look.

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Let's see what just one teaspoon
of salt can do.

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If we add one teaspoon of salt

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to this Olympic-size
swimming pool of ocean water,

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the ocean water stays ocean water.

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But if we add that same
one teaspoon of salt

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to this one-gallon jug
of fresh river water,

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suddenly, it becomes too salty to drink.

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So the point here is,

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because rivers, the volume is so small
compared to the oceans,

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it is especially vulnerable
to human activity,

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and we need to take care to protect them.

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So recently, I surveyed the literature

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to look at the river health
around the world.

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And I fully expected to see
ailing river health

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in regions of water scarcity
and heavy industrial development.

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And I saw that
in northern China and in India.

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But I was surprised
when I read a 2018 article

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where there's 232 river-sampling sites

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sampled across the United States.

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And of those sites,

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37 percent had increasing salinity levels.

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What was more surprising

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is that the ones
with the highest increases

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were found on the east part
of the United States,

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and not the arid southwest.

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The authors of this paper postulate

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that this could be due
to using salt to deice roads.

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Potentially, another source of this salt

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could come from salty
industrial wastewaters.

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So as you see, human activities
can convert our freshwater rivers

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into water that's more like our oceans.

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So we need to act and do something
before it's too late.

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And I have a proposal.

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We can take a three-step
river-defense mechanism,

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and if industrial-water users
practice this defense mechanism,

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we can put our rivers
in a much safer position.

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This involves, number one,

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extracting less water from our rivers

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by implementing water recycle
and reuse operations.

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Number two,

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we need to take the salt
out of these salty industrial wastewaters

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and recover it and reuse it
for other purposes.

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And number three,
we need to convert salt consumers,

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who currently source our salt from mines

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into salt consumers that source our salt
from recycled salt sources.

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This three-part defense mechanism
is already in play.

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This is what northern China
and India are implementing

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to help to rehabilitate the rivers.

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But the proposal here

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is to use this defense mechanism
to protect our rivers,

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so we don't need to rehabilitate them.

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And the good news is,
we have technology that can do this.

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It's with membranes.

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Membranes that can separate
salt and water.

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Membranes have been around
for a number of years,

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and they're based on polymeric materials
that separate based on size,

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or they can separate based on charge.

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The membranes that are used
to separate salt and water

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typically separate based on charge.

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And these membranes
are negatively charged,

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and help to repel the negatively
charged chloride ions

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that are in that dissolved salt.

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So, as I said, these membranes
have been around for a number of years,

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and currently, they are purifying
25 million gallons of water every minute.

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Even more than that, actually.

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But they can do more.

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These membranes are based
under the principle of reverse osmosis.

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Now osmosis is this natural process
that happens in our bodies --

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you know, how our cells work.

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And osmosis is where you have two chambers

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that separate two levels
of salt concentration.

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One with low salt concentration

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and one with high salt concentration.

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And separating the two chambers
is the semipermeable membrane.

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And under the natural osmosis process,

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what happens is the water naturally
transports across that membrane

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from the area of low salt concentration

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to the area of high salt concentration,

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until an equilibrium is met.

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Now reverse osmosis,
it's the reverse of this natural process.

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And in order to achieve this reversal,

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what we do is we apply a pressure
to the high-concentration side

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and in doing so, we drive the water
the opposite direction.

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And so the high-concentration side
becomes more salty,

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more concentrated,

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and the low-concentration side
becomes your purified water.

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So using reverse osmosis,
we can take an industrial wastewater

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and convert up to 95 percent of it
into pure water,

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leaving only five percent
as this concentrated salty mixture.

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Now, this five percent
concentrated salty mixture

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is not waste.

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So scientists have also
developed membranes

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that are modified to allow
some salts to pass through

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and not others.

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Using these membranes,

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which are commonly referred to
as nanofiltration membranes,

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now this five percent
concentrated salty solution

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can be converted
into a purified salt solution.

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So, in total, using reverse osmosis
and nanofiltration membranes,

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we can convert industrial wastewater

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into a resource of both water and salt.

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And in doing so,

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achieve pillars one and two
of this river-defense mechanism.

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Now, I've introduced this
to a number of industrial-water users,

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and the common response is,

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"Yeah, but who is going to use my salt?"

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So that's why pillar number three
is so important.

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We need to transform folks
that are using mine salt

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into consumers of recycled salt.

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So who are these salt consumers?

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Well, in 2018 in the United States,

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I learned that 43 percent of the salt
consumed in the US

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was used for road salt deicing purposes.

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Thirty-nine percent
was used by the chemical industry.

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So let's take a look
at these two applications.

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So, I was shocked.

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In the 2018-2019 winter season,

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one million tons of salt

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was applied to the roads
in the state of Pennsylvania.

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One million tons of salt is enough

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to fill two-thirds
of an Empire State Building.

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That's one million tons of salt
mined from the earth,

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applied to our roads,

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and then it washes off
into the environment and into our rivers.

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So the proposal here
is that we could at least

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source that salt from a salty
industrial wastewater,

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and prevent that
from going into our rivers,

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and rather use that to apply to our roads.

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So at least when the melt happens
in the springtime

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and you have this high-salinity runoff,

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the rivers are at least
in a better position

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to defend themselves against that.

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Now, as a chemist,

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the opportunity though
that I'm more psyched about

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is the concept of introducing
circular salt into the chemical industry.

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And the chlor-alkali industry is perfect.

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Chlor-alkali industry
is the source of epoxies,

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it's the source of urethanes and solvents

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and a lot of useful products
that we use in our everyday lives.

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And it uses sodium chloride salt
as its key feed stack.

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So the idea here is,

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well, first of all,
let's look at linear economy.

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So in a linear economy,
they're sourcing that salt from a mine,

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it goes through this chlor-alkali process,

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made into a basic chemical,

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which then can get converted
into another new product,

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or a more functional product.

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But during that conversion process,

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oftentimes salt is regenerated
as the by-product,

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and it ends up
in the industrial wastewater.

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So, the idea is that we can
introduce circularity,

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and we can recycle the water and salt
from those industrial wastewater streams,

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from the factories,

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and we can send it to the front end
of the chlor-alkali process.

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Circular salt.

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So how impactful is this?

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Well, let's just take one example.

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Fifty percent of the world's
production of propylene oxide

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is made through the chlor-alkali process.

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And that's a total of about five million
tons of propylene oxide

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on an annual basis, made globally.

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So that's five million tons of salt
mined from the earth

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converted through the chlor-alkali process
into propylene oxide,

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and then during that process,

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five million tons of salt
that ends up in wastewater streams.

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So five million tons

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is enough salt to fill
three Empire State Buildings.

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And that's on an annual basis.

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So you can see how circular salt
can provide a barrier

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to our rivers from this excessive
salty discharge.

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So you might wonder,

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"Well, gosh, these membranes
have been around for a number of years,

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so why aren't people implementing
wastewater reuse?

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Well, the bottom line is,

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it costs money to implement
wastewater reuse.

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And second,

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water in these regions is undervalued.

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Until it's too late.

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You know, if we don't plan
for freshwater sustainability,

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there are some severe consequences.

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You can just ask one of the world's
largest chemical manufacturers

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who last year took
a 280-million dollar hit

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due to low river levels
of the Rhine River in Germany.

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You can ask the residents
of Cape Town, South Africa,

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who experienced a year-over-year drought
drying up their water reserves,

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and then being asked
not to flush their toilets.

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So you can see,

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we have solutions here, with membranes,

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where we can provide pure water,

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we can provide pure salt,

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using these membranes, both of these,

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to help to protect our rivers
for future generations.

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Thank you.

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(Applause)