Growing up in northern Wisconsin,
I've naturally developed a connection
to the Mississippi River.
When I was little,
my sister and I would have contests
to see who could spell
"M-i-s-s-i-s-s-i-p-p-i" the fastest.
When I was in elementary school,
I got to learn about the early explorers
and their expeditions,
Marquette and Joliet, and how they used
the Great Lakes and the Mississippi River
and its tributaries
to discover the Midwest,
and to map a trade route
to the Gulf of Mexico.
In graduate school,
I was fortunate to have
the Mississippi River
outside my research laboratory window
at the University of Minnesota.
During that five-year period,
I got to know the Mississippi River.
I got to know its temperamental nature
and where it would flood
its banks at one moment,
and then shortly thereafter,
you would see its dry shorelines.
Today, as a physical organic chemist,
I'm committed to use my training
to help protect rivers,
like the Mississippi,
from excessive salt
that can come from human activity.
Because, you know,
salt is something that can contaminate
freshwater rivers.
And freshwater rivers,
they have only salt levels of .05 percent.
And at this level, it's safe to drink.
But the majority of the water
on our planet is housed in our oceans,
and ocean water has a salinity level
of more than three percent.
And if you drank that,
you'd be sick very quick.
So, if we are to compare
the relative volume of ocean water
to that of the river water
that's on our planet,
and let's say we are able
to put the ocean water
into an Olympic-size swimming pool,
then our planet's river water
would fit in a one-gallon jug.
So you can see it's a precious resource.
But do we treat it
like a precious resource?
Or rather, do we treat it
like that old rug
that you put in your front doorway
and wipe your feet off on it?
Treating rivers like that old rug
has severe consequences.
Let's take a look.
Let's see what just one teaspoon
of salt can do.
If we add one teaspoon of salt
to this Olympic-size
swimming pool of ocean water,
the ocean water stays ocean water.
But if we add that same
one teaspoon of salt
to this one-gallon jug
of fresh river water,
suddenly, it becomes too salty to drink.
So the point here is,
because rivers, the volume is so small
compared to the oceans,
it is especially vulnerable
to human activity,
and we need to take care to protect them.
So recently, I surveyed the literature
to look at the river health
around the world.
And I fully expected to see
ailing river health
in regions of water scarcity
and heavy industrial development.
And I saw that
in northern China and in India.
But I was surprised
when I read a 2018 article
where there's 232 river-sampling sites
sampled across the United States.
And of those sites,
37 percent had increasing salinity levels.
What was more surprising
is that the ones
with the highest increases
were found on the east part
of the United States,
and not the arid southwest.
The authors of this paper postulate
that this could be due
to using salt to deice roads.
Potentially, another source of this salt
could come from salty
industrial wastewaters.
So as you see, human activities
can convert our freshwater rivers
into water that's more like our oceans.
So we need to act and do something
before it's too late.
And I have a proposal.
We can take a three-step
river-defense mechanism,
and if industrial-water users
practice this defense mechanism,
we can put our rivers
in a much safer position.
This involves, number one,
extracting less water from our rivers
by implementing water recycle
and reuse operations.
Number two,
we need to take the salt
out of these salty industrial wastewaters
and recover it and reuse it
for other purposes.
And number three,
we need to convert salt consumers,
who currently source our salt from mines
into salt consumers that source our salt
from recycled salt sources.
This three-part defense mechanism
is already in play.
This is what northern China
and India are implementing
to help to rehabilitate the rivers.
But the proposal here
is to use this defense mechanism
to protect our rivers,
so we don't need to rehabilitate them.
And the good news is,
we have technology that can do this.
It's with membranes.
Membranes that can separate
salt and water.
Membranes have been around
for a number of years,
and they're based on polymeric materials
that separate based on size,
or they can separate based on charge.
The membranes that are used
to separate salt and water
typically separate based on charge.
And these membranes
are negatively charged,
and help to repel the negatively
charged chloride ions
that are in that dissolved salt.
So, as I said, these membranes
have been around for a number of years,
and currently, they are purifying
25 million gallons of water every minute.
Even more than that, actually.
But they can do more.
These membranes are based
under the principle of reverse osmosis.
Now osmosis is this natural process
that happens in our bodies --
you know, how our cells work.
And osmosis is where you have two chambers
that separate two levels
of salt concentration.
One with low salt concentration
and one with high salt concentration.
And separating the two chambers
is the semipermeable membrane.
And under the natural osmosis process,
what happens is the water naturally
transports across that membrane
from the area of low salt concentration
to the area of high salt concentration,
until an equilibrium is met.
Now reverse osmosis,
it's the reverse of this natural process.
And in order to achieve this reversal,
what we do is we apply a pressure
to the high-concentration side
and in doing so, we drive the water
the opposite direction.
And so the high-concentration side
becomes more salty,
more concentrated,
and the low-concentration side
becomes your purified water.
So using reverse osmosis,
we can take an industrial wastewater
and convert up to 95 percent of it
into pure water,
leaving only five percent
as this concentrated salty mixture.
Now, this five percent
concentrated salty mixture
is not waste.
So scientists have also
developed membranes
that are modified to allow
some salts to pass through
and not others.
Using these membranes,
which are commonly referred to
as nanofiltration membranes,
now this five percent
concentrated salty solution
can be converted
into a purified salt solution.
So, in total, using reverse osmosis
and nanofiltration membranes,
we can convert industrial wastewater
into a resource of both water and salt.
And in doing so,
achieve pillars one and two
of this river-defense mechanism.
Now, I've introduced this
to a number of industrial-water users,
and the common response is,
"Yeah, but who is going to use my salt?"
So that's why pillar number three
is so important.
We need to transform folks
that are using mine salt
into consumers of recycled salt.
So who are these salt consumers?
Well, in 2018 in the United States,
I learned that 43 percent of the salt
consumed in the US
was used for road salt deicing purposes.
Thirty-nine percent
was used by the chemical industry.
So let's take a look
at these two applications.
So, I was shocked.
In the 2018-2019 winter season,
one million tons of salt
was applied to the roads
in the state of Pennsylvania.
One million tons of salt is enough
to fill two-thirds
of an Empire State Building.
That's one million tons of salt
mined from the earth,
applied to our roads,
and then it washes off
into the environment and into our rivers.
So the proposal here
is that we could at least
source that salt from a salty
industrial wastewater,
and prevent that
from going into our rivers,
and rather use that to apply to our roads.
So at least when the melt happens
in the springtime
and you have this high-salinity runoff,
the rivers are at least
in a better position
to defend themselves against that.
Now, as a chemist,
the opportunity though
that I'm more psyched about
is the concept of introducing
circular salt into the chemical industry.
And the chlor-alkali industry is perfect.
Chlor-alkali industry
is the source of epoxies,
it's the source of urethanes and solvents
and a lot of useful products
that we use in our everyday lives.
And it uses sodium chloride salt
as its key feed stack.
So the idea here is,
well, first of all,
let's look at linear economy.
So in a linear economy,
they're sourcing that salt from a mine,
it goes through this chlor-alkali process,
made into a basic chemical,
which then can get converted
into another new product,
or a more functional product.
But during that conversion process,
oftentimes salt is regenerated
as the by-product,
and it ends up
in the industrial wastewater.
So, the idea is that we can
introduce circularity,
and we can recycle the water and salt
from those industrial wastewater streams,
from the factories,
and we can send it to the front end
of the chlor-alkali process.
Circular salt.
So how impactful is this?
Well, let's just take one example.
Fifty percent of the world's
production of propylene oxide
is made through the chlor-alkali process.
And that's a total of about five million
tons of propylene oxide
on an annual basis, made globally.
So that's five million tons of salt
mined from the earth
converted through the chlor-alkali process
into propylene oxide,
and then during that process,
five million tons of salt
that ends up in wastewater streams.
So five million tons
is enough salt to fill
three Empire State Buildings.
And that's on an annual basis.
So you can see how circular salt
can provide a barrier
to our rivers from this excessive
salty discharge.
So you might wonder,
"Well, gosh, these membranes
have been around for a number of years,
so why aren't people implementing
wastewater reuse?
Well, the bottom line is,
it costs money to implement
wastewater reuse.
And second,
water in these regions is undervalued.
Until it's too late.
You know, if we don't plan
for freshwater sustainability,
there are some severe consequences.
You can just ask one of the world's
largest chemical manufacturers
who last year took
a 280-million dollar hit
due to low river levels
of the Rhine River in Germany.
You can ask the residents
of Cape Town, South Africa,
who experienced a year-over-year drought
drying up their water reserves,
and then being asked
not to flush their toilets.
So you can see,
we have solutions here, with membranes,
where we can provide pure water,
we can provide pure salt,
using these membranes, both of these,
to help to protect our rivers
for future generations.
Thank you.
(Applause)
我在威斯康辛北部長大，
很自然和密西西比河
發展出了一種連結。
我小時候，
我和我姐姐會比賽誰能先拼出
「M-i-s-s-i-s-s-i-p-p-i
（密西西比）」。
我讀小學時，
我學到了早期的探險家
以及他們的探險，
馬凱特和喬利埃特，以及他們
如何透用五大湖及密西西比河
和它的支流，來發現美國中西部，
並將到墨西哥灣的
貿易路線畫成地圖。
在讀研究所時，
我很幸運，密西西比河
就在我的研究實驗室窗外，
那是在明尼蘇達大學。
在那五年期間，我有機會
認識了密西西比河。
我了解了它的無常特質，
可能這一刻它會將河岸淹沒，
沒多久之後，
你又能看見乾燥的河岸線。
現今，身為物理有機化學家，
我致力於發揮我的訓練
來協助保護河流，像密西西比河，
避免因為人類活動造成
河流的鹽份過高。
因為，
鹽有可能會汙染淡水河流。
淡水河流的鹽份含量只有0.05%。
鹽份在這個範圍內的水
可以安心飲用。
但地球上大部分的水在海洋裡，
海洋的鹽度超過3%。
如果飲用海水，你很快就會生病。
所以，若要將地球上的海洋水量
和河流水量來做相對比較，
假設我們能把海洋的水放到
奧運標準尺寸的遊泳池裡，
那麼地球上的河流水量
就可以放入一加侖的罐子中。
不難理解，河水是很珍貴的資源。
但我們有把它們當作
珍貴的資源來對待嗎？
或者，我們對待它們的方式，
就像對待鋪在大門口
用來擦拭腳下塵土的老地毯？
把河流當作老地毯來對待，
會有嚴重的後果。
咱們來看看。
咱們來看看一茶匙的鹽巴
會有什麼影響。
如果我們在一個奧運
標準尺寸的遊泳池裝滿海水，
再加進一茶匙的鹽巴，
海水還是海水。
但如果我們把同樣一茶匙的鹽巴
加到裝滿河流淡水的
一加侖罐子中，
突然，整罐水就變得
太鹹而無法飲用了。
這裡的重點是，因為
相對於海洋，河流的水量太少了，
河流很容易受到人類活動影響，
我們必須要照顧、保護河流。
最近，我調查文獻以
了解全世界各地河流的健康。
我完全預期會在水源稀少
和重度工業開發的區域
看到生病的河流。
我的確在中國北部和印度看到了。
但讓我意外的是，
我讀到一篇2018 年的文章，
文中提到，在全美國有
232 個河流抽樣站點。
在美國各地對河流抽樣。
在那些站點中，
有37% 發現鹽度上升。
更讓人驚訝的是，
鹽度增加最多的站點
是在美國東部，
而不是乾旱的西南部。
這篇文章的作者推測
原因可能是當地使用鹽
來避免道路結冰。
這些鹽份的另一個可能來源
是含鹽的工業廢水。
如各位所見，人類活動
可以將淡水河流轉變成
更像是海水的水。
我們必須要在太遲之前採取行動。
我有一個提議。
我們可以採用一個
三步驟的河流防禦機制，
如果工業水的使用者
能採用這種防禦機制，
我們就能讓河流更安全。
這機制的內容包括，第一，
導入水回收和再利用的做法，
來減少從河流取水。
第二，
我們必須要鹽份
從工業廢水中取出，
把取出的鹽份再利用至其他地方。
第三，我們得要將目前
使用礦鹽的消費者轉變成
使用回收鹽的消費者。
這個三步驟的防禦機制
已經在進行中了。
北中國和印度正是採用這個機制
來協助河流恢復原狀。
但，我提出的提議
是要用這個防禦機制
來保護我們的河流，
讓我們根本不用將河流恢復原狀。
好消息是，我們有技術
可以做到這一點。
這項技術是用薄膜。
可以把鹽和水分離的薄膜。
薄膜在很多年前就有了，
採用的是聚合材料，
依據體積來做分離，
也可以依據電荷來做分離。
用來將鹽和水分離的薄膜
通常是根據電荷來做分離的。
這些薄膜本身帶有負電，
能協助排斥溶解的鹽中
帶負電的氯離子。
我剛才說過，這些薄膜
在幾年前就有了，
目前，
它們每分鐘能淨化
兩千五百萬加侖的水。
實際上甚至還更多。
但它們能做的不只如此。
這些薄膜是以逆滲透原理為基礎。
滲透是我們身體中
會發生的自然過程——
和我們細胞的運作有關。
滲透作用就是有兩個不同的空間，
將兩種不同鹽份濃度給區別開來。
一邊是低鹽份濃度，
另一邊是高鹽份濃度。
將兩個空間隔開的是
一片半透性的薄膜。
在自然的滲透過程中，
水會很自然地通過那片薄膜，
從低鹽份濃度的地方
到高鹽份濃度的地方，
直到兩邊的濃度達到平衡。
逆滲透作用則是逆轉這個自然過程。
為了達成逆轉，
我們要做的是施加壓力給
高鹽份濃度的那一邊，
這麼做就能讓水
往相反的方向行進。
高鹽份濃度的那一邊，
鹽份會變得更高，
濃度更高，
而低鹽份濃度的那一邊
就變成了淨化的水。
利用逆滲透，我們可以
把95% 的工業廢水轉換成純水，
只留下5% 高鹽份濃度的混合物。
這5% 高鹽份濃度的
混合物並不是廢物。
科學家也開發出一些
改造過的薄膜，
讓某些鹽可以通過，
但其他的鹽不行。
用這種薄膜，
也就是一般所謂的奈米過濾膜，
這5% 的高鹽份濃度溶液
就能被轉換成純化的鹽溶液。
所以，總的來說，
有逆滲透作用和奈米過濾膜，
我們就能把工業廢水轉換
成為水和鹽的資源。
這麼做，
就能達成這個河流防禦機制的
第一和第二根支柱。
我曾向一些工業用水使用者
介紹過這個機制，
通常得到的反應是：
「好，但，誰會要用我的鹽？」
這就是為什麼
第三根支柱這麼重要。
我們必須要將使用
礦鹽的消費者轉型
成為使用回收鹽的消費者。
所以，誰是這些鹽的消費者？
2018 年，在美國，
我發現美國消費的鹽當中有43%
是用在防止道路結冰的用途上。
39% 是化學業在使用。
所以，咱們來談談這兩種應用。
我很震驚。
2018 年到2019 年的冬季，
一百萬噸的鹽
被用在賓州的道路上。
一百萬噸的鹽足以
裝滿帝國大廈的三分之二。
也就是從地球開採出了
一百萬噸的鹽，
用在我們的道路上，
接著這些鹽就被衝刷掉，
進入我們的環境和河流。
所以我的提議是，我們至少可以
從含鹽的工業廢水中取得那些鹽，
避免這些鹽進入我們的河流，
把它們用在我們的道路上。
至少，在春季開始融冰時，
出現高鹽度徑流時，
至少河流的狀況還會
比較有抵禦的能力。
身為化學家，
比較會讓我興奮的機會，
是把循環鹽導入
化學產業的這個概念。
氯鹼業是個完美的對象。
氯鹼業是環氧樹脂的來源，
也是氨基鉀酸酯、溶劑，
以及我們日常生活中
許多實用產品的來源。
該產業使用氯化鈉鹽
當作它的主要進料。
所以，這裡的想法是，
首先，咱們先來談談線性經濟。
在線性經濟中，鹽的來源是鹽礦，
它們會經過氯鹼過程，
被製成基本的化學製品，
這些化學製品能被
轉換成其他新產品，
或者更有功能性的產品。
但在轉換的過程中，
通常，都會重新生成鹽，
可算是副產品，
這些鹽最後會進入工業廢水中。
所以，我的想法是導入循環，
我們可以從工業廢水當中、
從工廠回收水和鹽，
再把它們送到氯鹼過程的前端。
循環鹽。
這會有多大的影響？
咱們用一個例子來說明。
全世界生產出的環氧丙烷，有50%
是透過氯鹼過程製造出來的。
也就是全球每年總共
約五百萬噸的環氧丙烷。
也就是從地球開採出
五百萬噸的鹽，
透過氯鹼過程轉換成環氧丙烷，
接著，在那過程中，
五百萬噸的鹽最後
會進入到廢水中。
五百萬噸的鹽可以
裝滿三棟帝國大廈。
那還只是一年的量。
這樣大家就可以了解，
為什麼循環鹽
可以協助我們的河流
抵禦過多的鹽排放。
各位可能會納悶：
「啊，很多年前就有這些薄膜了，
為什麼大家不去做廢水再利用？
嗯，基本上，
做廢水再利用是要花錢的。
第二，
在這些區域，水的價值被低估了。
直到太遲了。
如果我們不規劃淡水永續性，
將會有一些嚴重的後果。
你可以問世界上最大的化學製造商，
去年，他們因為德國
萊茵河水位過低，
受到了兩億八千萬美金的衝擊。
你可以問南非開普敦的居民，
他們遇到一年比一年嚴重的乾旱，
讓儲存的水被用盡，
接著被要求不可以衝馬桶。
所以，各位能了解，
我們有使用薄膜的解決方案，
用這個方案可以提供純水，
可以提供純鹽，
用這些薄膜，兩者都能提供，
為未來的世代保護我們的河流。
謝謝。
（掌聲）