A circular economy for salt that keeps rivers clean | Tina Arrowood

譯者: Lilian Chiu 審譯者: Melody Tang

Growing up in northern Wisconsin,

我在威斯康辛北部長大，

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

很自然和密西西比河 發展出了一種連結。

When I was little,

我小時候，

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

我和我姐姐會比賽誰能先拼出

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

「M-i-s-s-i-s-s-i-p-p-i （密西西比）」。

When I was in elementary school,

我讀小學時，

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

我學到了早期的探險家 以及他們的探險，

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

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

and its tributaries to discover the Midwest,

和它的支流，來發現美國中西部，

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

並將到墨西哥灣的 貿易路線畫成地圖。

In graduate school,

在讀研究所時，

I was fortunate to have the Mississippi River

我很幸運，密西西比河

outside my research laboratory window

就在我的研究實驗室窗外，

at the University of Minnesota.

那是在明尼蘇達大學。

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

在那五年期間，我有機會 認識了密西西比河。

I got to know its temperamental nature

我了解了它的無常特質，

and where it would flood its banks at one moment,

可能這一刻它會將河岸淹沒，

and then shortly thereafter,

沒多久之後，

you would see its dry shorelines.

你又能看見乾燥的河岸線。

Today, as a physical organic chemist,

現今，身為物理有機化學家，

I'm committed to use my training

我致力於發揮我的訓練

to help protect rivers, like the Mississippi,

來協助保護河流，像密西西比河，

from excessive salt that can come from human activity.

避免因為人類活動造成 河流的鹽份過高。

Because, you know,

因為，

salt is something that can contaminate freshwater rivers.

鹽有可能會污染淡水河流。

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

淡水河流的鹽份含量只有 0.05%。

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

鹽份在這個範圍內的水 可以安心飲用。

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

但地球上大部分的水在海洋裡，

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

海洋的鹽度超過 3%。

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

如果飲用海水，你很快就會生病。

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

所以，若要將地球上的海洋水量

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

和河流水量來做相對比較，

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

假設我們能把海洋的水放到

into an Olympic-size swimming pool,

奧運標準尺寸的游泳池裡，

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

那麼地球上的河流水量 就可以放入一加侖的罐子中。

So you can see it's a precious resource.

不難理解，河水是很珍貴的資源。

But do we treat it like a precious resource?

但我們有把它們當作 珍貴的資源來對待嗎？

Or rather, do we treat it like that old rug

或者，我們對待它們的方式，

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

就像對待舖在大門口 用來擦拭腳下塵土的老地毯？

Treating rivers like that old rug has severe consequences.

把河流當作老地毯來對待， 會有嚴重的後果。

Let's take a look.

咱們來看看。

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

咱們來看看一茶匙的鹽巴 會有什麼影響。

If we add one teaspoon of salt

如果我們在一個奧運 標準尺寸的游泳池裝滿海水，

to this Olympic-size swimming pool of ocean water,

再加進一茶匙的鹽巴，

the ocean water stays ocean water.

海水還是海水。

But if we add that same one teaspoon of salt

但如果我們把同樣一茶匙的鹽巴

to this one-gallon jug of fresh river water,

加到裝滿河流淡水的 一加侖罐子中，

suddenly, it becomes too salty to drink.

突然，整罐水就變得 太鹹而無法飲用了。

So the point here is,

這裡的重點是，因為

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

相對於海洋，河流的水量太少了，

it is especially vulnerable to human activity,

河流很容易受到人類活動影響，

and we need to take care to protect them.

我們必須要照顧、保護河流。

So recently, I surveyed the literature

最近，我調查文獻以

to look at the river health around the world.

了解全世界各地河流的健康。

And I fully expected to see ailing river health

我完全預期會在水源稀少

in regions of water scarcity and heavy industrial development.

和重度工業開發的區域 看到生病的河流。

And I saw that in northern China and in India.

我的確在中國北部和印度看到了。

But I was surprised when I read a 2018 article

但讓我意外的是， 我讀到一篇 2018 年的文章，

where there's 232 river-sampling sites

文中提到，在全美國有 232 個河流抽樣站點。

sampled across the United States.

在美國各地對河流抽樣。

And of those sites,

在那些站點中，

37 percent had increasing salinity levels.

有 37% 發現鹽度上升。

What was more surprising

更讓人驚訝的是，

is that the ones with the highest increases

鹽度增加最多的站點

were found on the east part of the United States,

是在美國東部，

and not the arid southwest.

而不是乾旱的西南部。

The authors of this paper postulate

這篇文章的作者推測

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

原因可能是當地使用鹽 來避免道路結冰。

Potentially, another source of this salt

這些鹽份的另一個可能來源

could come from salty industrial wastewaters.

是含鹽的工業廢水。

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

如各位所見，人類活動 可以將淡水河流轉變成

into water that's more like our oceans.

更像是海水的水。

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

我們必須要在太遲之前採取行動。

And I have a proposal.

我有一個提議。

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

我們可以採用一個 三步驟的河流防禦機制，

and if industrial-water users practice this defense mechanism,

如果工業水的使用者 能採用這種防禦機制，

we can put our rivers in a much safer position.

我們就能讓河流更安全。

This involves, number one,

這機制的內容包括，第一，

extracting less water from our rivers

導入水回收和再利用的做法，

by implementing water recycle and reuse operations.

來減少從河流取水。

Number two,

第二，

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

我們必須要鹽份 從工業廢水中取出，

and recover it and reuse it for other purposes.

把取出的鹽份再利用至其他地方。

And number three, we need to convert salt consumers,

第三，我們得要將目前

使用礦鹽的消費者轉變成

who currently source our salt from mines

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

使用回收鹽的消費者。

This three-part defense mechanism is already in play.

這個三步驟的防禦機制 已經在進行中了。

This is what northern China and India are implementing

北中國和印度正是採用這個機制

to help to rehabilitate the rivers.

來協助河流恢復原狀。

But the proposal here

但，我提出的提議

is to use this defense mechanism to protect our rivers,

是要用這個防禦機制 來保護我們的河流，

so we don't need to rehabilitate them.

讓我們根本不用將河流恢復原狀。

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

好消息是，我們有技術 可以做到這一點。

It's with membranes.

這項技術是用薄膜。

Membranes that can separate salt and water.

可以把鹽和水分離的薄膜。

Membranes have been around for a number of years,

薄膜在很多年前就有了，

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

採用的是聚合材料， 依據體積來做分離，

or they can separate based on charge.

也可以依據電荷來做分離。

The membranes that are used to separate salt and water

用來將鹽和水分離的薄膜

typically separate based on charge.

通常是根據電荷來做分離的。

And these membranes are negatively charged,

這些薄膜本身帶有負電，

and help to repel the negatively charged chloride ions

能協助排斥溶解的鹽中

that are in that dissolved salt.

帶負電的氯離子。

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

我剛才說過，這些薄膜 在幾年前就有了，

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

目前，

它們每分鐘能淨化 兩千五百萬加侖的水。

Even more than that, actually.

實際上甚至還更多。

But they can do more.

但它們能做的不只如此。

These membranes are based under the principle of reverse osmosis.

這些薄膜是以逆滲透原理為基礎。

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

滲透是我們身體中 會發生的自然過程——

you know, how our cells work.

和我們細胞的運作有關。

And osmosis is where you have two chambers

滲透作用就是有兩個不同的空間，

that separate two levels of salt concentration.

將兩種不同鹽份濃度給區別開來。

One with low salt concentration

一邊是低鹽份濃度，

and one with high salt concentration.

另一邊是高鹽份濃度。

And separating the two chambers is the semipermeable membrane.

將兩個空間隔開的是 一片半透性的薄膜。

And under the natural osmosis process,

在自然的滲透過程中，

what happens is the water naturally transports across that membrane

水會很自然地通過那片薄膜，

from the area of low salt concentration

從低鹽份濃度的地方 到高鹽份濃度的地方，

to the area of high salt concentration,

until an equilibrium is met.

直到兩邊的濃度達到平衡。

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

逆滲透作用則是逆轉這個自然過程。

And in order to achieve this reversal,

為了達成逆轉，

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

我們要做的是施加壓力給 高鹽份濃度的那一邊，

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

這麼做就能讓水 往相反的方向行進。

And so the high-concentration side becomes more salty,

高鹽份濃度的那一邊， 鹽份會變得更高，

more concentrated,

濃度更高，

and the low-concentration side becomes your purified water.

而低鹽份濃度的那一邊 就變成了淨化的水。

So using reverse osmosis, we can take an industrial wastewater

利用逆滲透，我們可以

把 95% 的工業廢水轉換成純水，

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

leaving only five percent as this concentrated salty mixture.

只留下 5% 高鹽份濃度的混合物。

Now, this five percent concentrated salty mixture

這 5% 高鹽份濃度的 混合物並不是廢物。

is not waste.

So scientists have also developed membranes

科學家也開發出一些 改造過的薄膜，

that are modified to allow some salts to pass through

讓某些鹽可以通過，

and not others.

但其他的鹽不行。

Using these membranes,

用這種薄膜，

which are commonly referred to as nanofiltration membranes,

也就是一般所謂的奈米過濾膜，

now this five percent concentrated salty solution

這 5% 的高鹽份濃度溶液

can be converted into a purified salt solution.

就能被轉換成純化的鹽溶液。

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

所以，總的來說， 有逆滲透作用和奈米過濾膜，

we can convert industrial wastewater

我們就能把工業廢水轉換

into a resource of both water and salt.

成為水和鹽的資源。

And in doing so,

這麼做，

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

就能達成這個河流防禦機制的 第一和第二根支柱。

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

我曾向一些工業用水使用者 介紹過這個機制，

and the common response is,

通常得到的反應是：

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

「好，但，誰會要用我的鹽？」

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

這就是為什麼 第三根支柱這麼重要。

We need to transform folks that are using mine salt

我們必須要將使用 礦鹽的消費者轉型

into consumers of recycled salt.

成為使用回收鹽的消費者。

So who are these salt consumers?

所以，誰是這些鹽的消費者？

Well, in 2018 in the United States,

2018 年，在美國，

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

我發現美國消費的鹽當中有 43%

was used for road salt deicing purposes.

是用在防止道路結冰的用途上。

Thirty-nine percent was used by the chemical industry.

39% 是化學業在使用。

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

所以，咱們來談談這兩種應用。

So, I was shocked.

我很震驚。

In the 2018-2019 winter season,

2018 年到 2019 年的冬季，

one million tons of salt

一百萬噸的鹽

was applied to the roads in the state of Pennsylvania.

被用在賓州的道路上。

One million tons of salt is enough

一百萬噸的鹽足以

to fill two-thirds of an Empire State Building.

裝滿帝國大廈的三分之二。

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

也就是從地球開採出了 一百萬噸的鹽，

applied to our roads,

用在我們的道路上，

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

接著這些鹽就被沖刷掉， 進入我們的環境和河流。

So the proposal here is that we could at least

所以我的提議是，我們至少可以

source that salt from a salty industrial wastewater,

從含鹽的工業廢水中取得那些鹽，

and prevent that from going into our rivers,

避免這些鹽進入我們的河流，

and rather use that to apply to our roads.

把它們用在我們的道路上。

So at least when the melt happens in the springtime

至少，在春季開始融冰時，

and you have this high-salinity runoff,

出現高鹽度逕流時，

the rivers are at least in a better position

至少河流的狀況還會

to defend themselves against that.

比較有抵禦的能力。

Now, as a chemist,

身為化學家，

the opportunity though that I'm more psyched about

比較會讓我興奮的機會，

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

是把循環鹽導入 化學產業的這個概念。

And the chlor-alkali industry is perfect.

氯鹼業是個完美的對象。

Chlor-alkali industry is the source of epoxies,

氯鹼業是環氧樹脂的來源，

it's the source of urethanes and solvents

也是氨基鉀酸酯、溶劑，

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

以及我們日常生活中 許多實用產品的來源。

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

該產業使用氯化鈉鹽 當作它的主要進料。

So the idea here is,

所以，這裡的想法是，

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

首先，咱們先來談談線性經濟。

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

在線性經濟中，鹽的來源是鹽礦，

it goes through this chlor-alkali process,

它們會經過氯鹼過程，

made into a basic chemical,

被製成基本的化學製品，

which then can get converted into another new product,

這些化學製品能被 轉換成其他新產品，

or a more functional product.

或者更有功能性的產品。

But during that conversion process,

但在轉換的過程中，

oftentimes salt is regenerated as the by-product,

通常，都會重新生成鹽， 可算是副產品，

and it ends up in the industrial wastewater.

這些鹽最後會進入工業廢水中。

So, the idea is that we can introduce circularity,

所以，我的想法是導入循環，

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

我們可以從工業廢水當中、

從工廠回收水和鹽，

from the factories,

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

再把它們送到氯鹼過程的前端。

Circular salt.

循環鹽。

So how impactful is this?

這會有多大的影響？

Well, let's just take one example.

咱們用一個例子來說明。

Fifty percent of the world's production of propylene oxide

全世界生產出的環氧丙烷，有 50%

is made through the chlor-alkali process.

是透過氯鹼過程製造出來的。

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

也就是全球每年總共

約五百萬噸的環氧丙烷。

on an annual basis, made globally.

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

也就是從地球開採出 五百萬噸的鹽，

converted through the chlor-alkali process into propylene oxide,

透過氯鹼過程轉換成環氧丙烷，

and then during that process,

接著，在那過程中，

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

五百萬噸的鹽最後 會進入到廢水中。

So five million tons

五百萬噸的鹽可以 裝滿三棟帝國大廈。

is enough salt to fill three Empire State Buildings.

And that's on an annual basis.

那還只是一年的量。

So you can see how circular salt can provide a barrier

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。

to our rivers from this excessive salty discharge.

So you might wonder,

各位可能會納悶：

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

「啊，很多年前就有這些薄膜了，

so why aren't people implementing wastewater reuse?

為什麼大家不去做廢水再利用？

Well, the bottom line is,

嗯，基本上，

it costs money to implement wastewater reuse.

做廢水再利用是要花錢的。

And second,

第二，

water in these regions is undervalued.

在這些區域，水的價值被低估了。

Until it's too late.

直到太遲了。

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

如果我們不規劃淡水永續性，

there are some severe consequences.

將會有一些嚴重的後果。

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

你可以問世界上最大的化學製造商，

who last year took a 280-million dollar hit

去年，他們因為德國 萊茵河水位過低，

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

受到了兩億八千萬美金的衝擊。

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

你可以問南非開普敦的居民，

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

他們遇到一年比一年嚴重的乾旱， 讓儲存的水被用盡，

and then being asked not to flush their toilets.

接著被要求不可以沖馬桶。

So you can see,

所以，各位能了解，

we have solutions here, with membranes,

我們有使用薄膜的解決方案，

where we can provide pure water,

用這個方案可以提供純水，

we can provide pure salt,

可以提供純鹽，

using these membranes, both of these,

用這些薄膜，兩者都能提供，

to help to protect our rivers for future generations.

為未來的世代保護我們的河流。

Thank you.

謝謝。

(Applause)

（掌聲）