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

翻译人员: Yanyan Hong 校对人员: Yolanda Zhang

Growing up in northern Wisconsin,

我在威斯康星州北部长大，

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

很自然地与密西西比河 产生了亲密的连结。

When I was little,

小时候，

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

我会和姐姐比赛谁能最先拼写出

"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,

上小学时，

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

我学到了早期的探险家 以及他们的冒险，

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

马奎特和朱莉特，以及他们是 如何通过五大湖，密西西比河

and its tributaries to discover the Midwest,

及其支流，发现了美国中西部，

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

并将到墨西哥湾的贸易路线画成了地图。

In graduate school,

在读研究生时，

I was fortunate to have the Mississippi River

我很幸运，密西西比河正好

outside my research laboratory window

就在我所在的明尼苏达大学

at the University of Minnesota.

研究实验室窗外。

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

在那五年期间， 我有机会认识了密西西比河，

I got to know its temperamental nature

我发掘了它无与伦比的特质，

and where it would flood its banks at one moment,

可能某一刻它会将河岸淹没，

and then shortly thereafter,

不久后，

you would see its dry shorelines.

干燥的河岸线又清晰可见了。

Today, as a physical organic chemist,

今天，作为一位物理有机化学家，

I'm committed to use my training

我致力于利用我所学，

to help protect rivers, like the Mississippi,

来保护像密西西比河这样的河流，

from excessive salt that can come from human activity.

避免因为人类的活动， 而造成河流盐分升高。

Because, you know,

因为

salt is something that can contaminate freshwater rivers.

盐分会污染淡水河流。

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

淡水河流的盐分含量只有 0.05 %，

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

盐分在这个范围内的水可以安全饮用。

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

但地球上大部分的水来自我们的海洋，

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

而海洋的盐含量超过 3%，

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

如果饮用海水，你很快就会生病。

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

所以若要将地球上所有的海水

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

和河流水量相比较，

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

假设我们把海水放进

into an Olympic-size swimming pool,

奥运标准游泳池中，

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

那么地球上的河流水量 就相当于一加仑。

So you can see it's a precious resource.

所以不难想到， 这是弥足珍贵的资源。

But do we treat it like a precious resource?

可是我们有把它当作 珍贵的资源来对待吗？

Or rather, do we treat it like that old rug

或者，我们对待它的方式， 就像对待铺在大门口的

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

老式地毯，顶多用来擦擦鞋？

Treating rivers like that old rug has severe consequences.

把河流当作老地毯会导致严重的后果，

Let's take a look.

我们来看看。

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

我们来看看一茶勺的 盐会有什么影响，

If we add one teaspoon of salt

如果我们在一个装满 海水的奥运会标准泳池中

to this Olympic-size swimming pool of ocean water,

加入一勺盐，

the ocean water stays ocean water.

海水依然是海水，

But if we add that same one teaspoon of salt

但是再加进同样一茶勺的盐

to this one-gallon jug of fresh river water,

到一加仑干净河水中，

suddenly, it becomes too salty to drink.

一下子整罐水就因太咸而无法饮用。

So the point here is,

重点是因为，

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

相比海洋，河流的水太稀少了，

it is especially vulnerable to human activity,

它很容易受到人类活动的影响，

and we need to take care to protect them.

而我们需要小心地保护河流。

So recently, I surveyed the literature

最近，我通过调查文献，

to look at the river health around the world.

了解了全世界各地的河流健康问题，

And I fully expected to see ailing river health

我完全预期会在水源稀少，

in regions of water scarcity and heavy industrial development.

以及重度工业发展区看到“生病”的河流。

And I saw that in northern China and in India.

我的确在中国北部和印度看到了。

But I was surprised when I read a 2018 article

但让我意外的是， 在一篇 2018 年最新的文章中，

where there's 232 river-sampling sites

提到在全美有 232 个河流抽样站点，

sampled across the United States.

对美国各地河流抽样，

And of those sites,

这些站点显示，

37 percent had increasing salinity levels.

在 37% 的地方发现盐度超标。

What was more surprising

更让人惊讶的是，

is that the ones with the highest increases

盐度增加最多的站点

were found on the east part of the United States,

在美国东部，

and not the arid southwest.

而不是干旱的西南部。

The authors of this paper postulate

这篇文章的作者推测，

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

原因可能是因为当地使用 盐来应对道路结冰问题，

Potentially, another source of this salt

另一个可能来源是

could come from salty industrial wastewaters.

含盐的工业废水。

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

如你所见，人类的活动 可能让干净的河流变成

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.

所以我们必须尽快行动起来。

And I have a proposal.

我有一项提议。

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

我们可以采取一个 三步计划预防河流污染，

and if industrial-water users practice this defense mechanism,

如果工业水的排放者 能采取这个预防步骤，

we can put our rivers in a much safer position.

我们就可以让河流更安全。

This involves, number one,

此内容包括，第一，

extracting less water from our rivers

导入水回收和再利用的方法，

by implementing water recycle and reuse operations.

从而减少河流取水。

Number two,

第二，

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

我们必须将盐分 从工业水中提取出来，

and recover it and reuse it for other purposes.

再利用到其他地方。

And number three, we need to convert salt consumers,

第三，我们要将目前

who currently source our salt from mines

使用岩盐的消费者转变成

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

使用回收盐的消费者。

This three-part defense mechanism is already in play.

这三个步骤的处理方法已在实施，

This is what northern China and India are implementing

中国北部和印度正在

to help to rehabilitate the rivers.

采用这一机制来补救河流。

But the proposal here

但我提出的意见是，

is to use this defense mechanism to protect our rivers,

要用这个预防机制 来保护我们的河流，

so we don't need to rehabilitate them.

这样就不需要事后再补救。

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

好消息是，我们可以使用薄膜技术

It's with membranes.

来实现。

Membranes that can separate salt and water.

这种薄膜可以把盐和水分离开。

Membranes have been around for a number of years,

薄膜在很多年前就已存在，

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

采用的是聚合材料， 依据体积来进行物质分离，

or they can separate based on charge.

也可以依据电荷来做分离。

The membranes that are used to separate salt and water

用来将盐和水分离的薄膜，

typically separate based on charge.

通常是根据电荷来做分离。

And these membranes are negatively charged,

这些薄膜本身带有负电荷，

and help to repel the negatively charged chloride ions

能协助排斥溶解盐中

that are in that dissolved salt.

带负电荷的氯离子。

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

我刚才提到，这些薄膜 在很多年前就有了，

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

目前，它们每分钟能 净化两千五百万加仑的水。

Even more than that, actually.

甚至更多。

But they can do more.

但是它们能做的远不只这些。

These membranes are based under the principle of reverse osmosis.

这些薄膜是以渗透原理为基础的。

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

渗透是我们身体中 会发生的自然过程——

you know, how our cells work.

和细胞的工作原理有关。

And osmosis is where you have two chambers

渗透作用就是有两个不同的空间，

that separate two levels of salt concentration.

将两种不同浓度的盐溶液分开，

One with low salt concentration

一份是低盐度，

and one with high salt concentration.

另一份是高盐度。

And separating the two chambers is the semipermeable membrane.

将两个空间隔开的是 一张半渗透性的薄膜。

And under the natural osmosis process,

在自然渗透的过程中，

what happens is the water naturally transports across that membrane

水会很自然的通过薄膜，

from the area of low salt concentration

从低盐份浓度的地方

to the area of high salt concentration,

流动到高盐度浓度的地方，

until an equilibrium is met.

直到两边的浓度达到平衡。

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

逆渗透作用则是逆转这个过程。

And in order to achieve this reversal,

为了实现逆转，

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

我们就要施加压力 给高浓度的那一端，

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

这么做就能让水往反方向流动。

And so the high-concentration side becomes more salty,

高浓度的那一端含盐量会增加，

more concentrated,

浓度更高，

and the low-concentration side becomes your purified water.

而低浓度那一端 则会变成净化过的水。

So using reverse osmosis, we can take an industrial wastewater

利用逆渗透方法， 我们可以把 95%

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

的工业用水转化为干净的水，

leaving only five percent as this concentrated salty mixture.

只留下 5% 高浓度的盐混合物。

Now, this five percent concentrated salty mixture

而这 5% 高盐浓度的混合物

is not waste.

并非废物。

So scientists have also developed membranes

科学家也研发出了改造过的薄膜，

that are modified to allow some salts to pass through

让某些盐可以通过，

and not others.

而其他的不行。

Using these membranes,

使用这些薄膜，

which are commonly referred to as nanofiltration membranes,

也就是我们熟知的纳米过滤膜，

now this five percent concentrated salty solution

这 5% 的高浓度溶液，

can be converted into a purified salt solution.

就能被转化成纯盐溶液，

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

所以，总的来说， 有了逆渗透技术和纳米薄膜，

we can convert industrial wastewater

我们就能把工业废水

into a resource of both water and salt.

转化成水和盐，

And in doing so,

这样一来，

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

就能实现河流保护机制 的第一和第二步。

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

我曾向一些工业水 使用者介绍了这个机制，

and the common response is,

通常得到的反馈是，

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

“不错啊，但是谁会要我的盐呢？”

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

这就是为什么第三步很关键，

We need to transform folks that are using mine salt

我们必须要将使用岩盐的消费者，

into consumers of recycled salt.

转化为使用回收盐的消费者，

So who are these salt consumers?

那么这些消费者是谁呢？

Well, in 2018 in the United States,

2018 年，

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

我发现美国消费盐的人当中 43%

was used for road salt deicing purposes.

都是把盐用在防止道路结冰上。

Thirty-nine percent was used by the chemical industry.

39% 是化学工业在使用。

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

我们来看看这两种应用。

So, I was shocked.

我很震惊，

In the 2018-2019 winter season,

在 2018 年到 2019 年冬季，

one million tons of salt

一百万吨的盐被用在

was applied to the roads in the state of Pennsylvania.

宾夕法尼亚州的道路上。

One million tons of salt is enough

一百万吨的盐足以

to fill two-thirds of an Empire State Building.

装满三分之二的帝国大厦。

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

也就是说从地球上 开采出了一百万吨的盐，

applied to our roads,

用于我们的道路，

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

接着这些盐就 被冲刷进了我们的河流。

So the proposal here is that we could at least

所以我的提议是，至少我们可以

source that salt from a salty industrial wastewater,

从含盐的工业废水中提取那些盐，

and prevent that from going into our rivers,

避免这些盐进入我们的河流，

and rather use that to apply to our roads.

把它们使用在我们的道路上。

So at least when the melt happens in the springtime

这样至少在春季融冰之时，

and you have this high-salinity runoff,

出现高盐度的径流时，

the rivers are at least in a better position

我们的河流状况会更好，

to defend themselves against that.

可以有强的抵抗能力。

Now, as a chemist,

身为一名化学家，

the opportunity though that I'm more psyched about

更让我激动的机会是

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

把循环盐导入化学工业这个概念。

And the chlor-alkali industry is perfect.

氯碱工业是个理想的对象，

Chlor-alkali industry is the source of epoxies,

它是环氧树脂的来源，

it's the source of urethanes and solvents

也是聚氨酯和各种溶剂，

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

以及我们日常生活中 许多实用产品的来源。

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

该产业使用氯化钠盐 作为主要的原材料。

So the idea here is,

所以我的想法是——

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

首先，我们先来谈谈线性经济。

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

在线性经济中， 人们从一个矿里找盐，

it goes through this chlor-alkali process,

它会经历这个氯碱过程，

made into a basic chemical,

被制成基本的化学物质，

which then can get converted into another new product,

接着又被转换成其他新的产品，

or a more functional product.

或者更有功能性的产品，

But during that conversion process,

但在转换过程中，

oftentimes salt is regenerated as the by-product,

通常都会重新 生成盐，算是副产品，

and it ends up in the industrial wastewater.

这些盐也会进入工业废水。

So, the idea is that we can introduce circularity,

所以，我们可以导入循环，

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

从工厂回收工业废水中

from the factories,

的水和盐，

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

再把它送到氯碱处理的前端。

Circular salt.

这就是循环盐。

So how impactful is this?

那么这会有多大的影响呢？

Well, let's just take one example.

让我举个例子。

Fifty percent of the world's production of propylene oxide

全世界的环氧丙烷有 50%

is made through the chlor-alkali process.

是通过氯碱过程制作出来的，

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

也就是全球每年总共生产

on an annual basis, made globally.

约五百万吨的环氧丙烷。

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

那么，从地球开采的五百万吨盐，

converted through the chlor-alkali process into propylene oxide,

通过氯碱过程转换成环氧丙烷，

and then during that process,

在这个过程中，

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

五百万吨的盐最后会进入废水中。

So five million tons

五百万吨的盐

is enough salt to fill three Empire State Buildings.

足以填满三个帝国大厦，

And that's on an annual basis.

那还只是一年的量。

So you can see how circular salt can provide a barrier

这样大家就可以了解到 为什么循环盐

to our rivers from this excessive salty discharge.

可以帮助我们的河流 抵御过多的盐排放。

So you might wonder,

各位可能会纳闷，

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

“哦，天呐，很多年 以前就有这些薄膜了，

so why aren't people implementing wastewater reuse?

为什么大家都不去做 废水循环利用呢？

Well, the bottom line is,

根本原因就是，

it costs money to implement wastewater reuse.

做废水再利用需要资金。

And second,

其次，

water in these regions is undervalued.

在这些区域水的价值被低估了，

Until it's too late.

没有及时进行循环再利用。

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

如果我们不规划淡水的可持续性，

there are some severe consequences.

就将要面临严重的后果。

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

可以问问世界上最大的化学品制造商，

who last year took a 280-million dollar hit

去年，他们因为德国莱茵河水位过低，

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

遭受了 2 亿 8 千万美金的损失，

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

也可以问问南非开普敦的人民，

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

他们遇到了一年比一年严重的干旱， 让所有储存的水被耗尽，

and then being asked not to flush their toilets.

甚至被限制冲马桶，以节省水源。

So you can see,

所以我们可以看到，

we have solutions here, with membranes,

现在我们有解决办法，那就是薄膜，

where we can provide pure water,

用这个方法可以得到纯净水，

we can provide pure salt,

得到纯盐，

using these membranes, both of these,

一石二鸟。

to help to protect our rivers for future generations.

为未来的世代，保护我们的河流吧。

Thank you.

谢谢。

(Applause)

（掌声）