Would you rather drink this water, or this water?

你願意喝這個水，還是這個水？

Well, of course you would choose the water on the left

那你當然會選擇左邊的水了

Unfortunately, some people in other parts of the world have no choice at all

不幸的是，世界上其他地方的一些人別無選擇。

Did you know that small floating particles in drinking water can

您是否知道飲用水中的小漂浮顆粒可以

make you sick? Imagine we have a super powerful microscope and we can

讓你生病？想象一下，我們有一個超級強大的顯微鏡，我們可以。

zoom into the water. ZOOM!

放大到水中。ZOOM！

What will we find? What are these small, floating particles,

我們會發現什麼？這些漂浮的小顆粒是什麼。

and how do they float? These particles are of two types:

以及它們是如何漂浮的？這些顆粒有兩種類型。

inorganic (like clay, silt, and mineral oxides) and

無機物（如粘土、淤泥和礦物氧化物）和

organic (such as algae, protozoa, and bacteria).

有機物（如藻類、原生動物和細菌）；

The bacteria, once ingested by humans, can sometimes be fatal.

這種細菌一旦被人類攝入，有時會致命。

All of these small particles are able to float, because they are not heavy enough

所有這些小顆粒都能漂浮起來，因為它們不夠重。

to settle to the bottom by gravity. Suspended particles that are too

在重力作用下沉入海底。懸浮顆粒如果太大

light and small to settle are called colloids.

輕而小的沉降稱為膠體。

When looked at together, these colloids cause a state of cloudiness

當這些膠體一起看時，會造成一種渾濁的狀態。

or haziness, known as turbidity. The more cloudy a fluid looks, the more

或朦朧感，稱為濁度。液體看起來越渾濁，就越是

turbid it is. Here we see four beakers of

它是渾濁的。在這裡，我們看到四個燒杯的

water with increasing levels of turbidity, from left to right.

水的渾濁程度越來越高，從左到右。

There is a relation between turbidity and the risk of getting a disease.

渾濁度和得病的風險是有關係的。

Science shows that the more turbid

科學表明，越是渾濁的

the drinking water is, the higher the risk of getting sick is.

飲水越多，生病的風險越大。

Now why is this? This is because toxic compounds can

現在為什麼會這樣呢？這是因為有毒化合物可以

adsorb, that is, stick to the surface of the suspended colloids.

吸附，即粘附在懸浮膠體的表面。

The more colloids there are, the more toxic the water can become.

膠體越多，水的毒性就越大。

These toxic materials and bacteria can cause cholera,

這些有毒物質和細菌可以引起霍亂。

salmonellosis, hepatitis A, dysentery,

沙門氏菌病、A肝、痢疾。

and e-coli infection. These illnesses effect and kill

和大腸桿菌感染。這些疾病影響和殺死

millions of people a year, and are especially dangerous to children, whose weak

每年有數以百萬計的人死亡，對兒童尤其危險，因為他們的身體虛弱。

immune systems cannot provide an adequate defense.

免疫系統無法提供足夠的防禦。

Fortunately, we can do something about this! One of the very

幸運的是，我們可以做一些事情!其中一個非常

practical ways to clean this turbid water is called flocculation

清理這種渾濁的水的實用方法叫做絮凝法

Flocculation is the process in which colloids aggregate,

絮凝是膠體聚集的過程。

or come together to form larger particles called flocks, by the addition

或聚集在一起形成更大的顆粒，稱為羊群，通過添加。

of a chemical called a flocculant. Typical flocculants

稱為絮凝劑的化學物質。典型的絮凝劑

include Alum and Ferrix, because they work well with high turbidity fluid mixtures

包括Alum和Ferrix，因為它們能很好地處理高濁度流體混合物。

Now, let's demonstrate how flocculation works. First, we'll need

現在，讓我們來演示一下絮凝的工作原理。首先，我們需要

to go out and collect some muddy water from the Charles River

去收集一些查爾斯河的泥水。

Here are two beakers filled with the same amount of muddy Charles River water

這裡有兩個燒杯，裝滿了同樣數量的查爾斯河泥水。

On the left is our control, which will remain untouched,

左邊是我們的控制權，它將保持不受影響。

and on the right, we'll add 3mL of prepared flocculant solution

在右邊，我們將添加3mL準備好的絮凝劑溶液。

Then we'll stir for two minutes, and wait

然後我們會攪拌兩分鐘，然後等待。

Wow! What just happened?

哇！剛剛發生了什麼？

The colloids in the turbid water on the left may never settle

左邊濁水中的膠體可能永遠不會沉澱下來

whereas, with the addition of just a little bit of flocculant

而只要加一點絮凝劑

the water on the right became clear.

右邊的水變得清澈起來。

In order to make this water potable, it will require skimming and filtration

為了使這些水可以飲用，需要進行脫脂和過濾。

and maybe some additional treatment

也許還需要一些額外的治療

If you're wondering what's going on, let's explain how this flocculant business works.

如果你'想知道是怎麼回事，讓我們'來解釋一下這個絮凝劑業務是如何工作的。

Almost all colloids have negatively charged surfaces

幾乎所有的膠體都有帶負電的表面。

This means that positive ions, or charged particles in water

這意味著，正離子，或水中的帶電粒子。

will attract to the colloid surface, forming a first layer.

將吸引到膠體表面，形成第一層。

Recall how like poles of a magnet will repel, while opposite poles will attract.

回想一下磁鐵的同類極性會排斥，而相反極性會吸引。

The same occurs with colloids in water.

水中的膠體也是如此。

A diffuse layer, made up of a mix of positive and negative ions will then surround the first

然後，由正負離子混合組成的擴散層將包圍第一層。

forming what is called a double layer.

形成所謂的雙層。

This double layer provides a repulsive force which prevents two colloids from sticking to each other.

這種雙層提供了一種排斥力，防止兩個膠體相互粘連。

Once the flocculant is added, it adheres to the surfaces of the particles,

一旦加入絮凝劑，它就會附著在顆粒的表面。

compressing the double layer,

壓縮雙層。

and allowing the colloids to stick to each other and form "flocks"

並讓膠體相互粘連，形成"群&quot。

These flocks are now heavy enough to settle to the bottom by gravity.

這些羊群現在已經很重了，可以靠重力沉澱到底部。

Given how effective flocculation is, many countries around the world

鑑於絮凝的效果，世界上許多國家

use this method for cleaning their water supplies.

使用這種方法來清洗他們的供水。

Did you know that Singapore, for instance, produces drinking water from sewer water

你知道嗎，比如新加坡，用下水道的水生產飲用水。

using a number of methods, including flocculation?

採用多種方法，包括絮凝?

As the global population increases

隨著全球人口的增加

and freshwater resources become more and more scarce

淡水資源越來越稀缺的問題。

flocculation is one tool that can supply clean, healthy, and tasty drinking water

絮凝是一種可以提供清潔、健康和美味飲用水的工具。

worldwide.

在全球範圍內，