How the water you flush becomes the water you drink - Francis de los Reyes

翻译人员: Jacky He 校对人员: suya f.

In 2003, Singapore’s national water agency launched an unprecedented program.

2003 年，新加坡的国家水利部门 启动了一项前所未有的项目。

Using two new facilities,

依靠两所新设施，

they planned to provide more than 50% of their nation’s water supply

它计划通过处理废水提供国家

by recycling wastewater.

超过 50% 的水资源。

And yes, we do mean that wastewater.

是的，是这种废水。

While this might seem like a desperate decision,

虽然这似乎是不得已的举措，

this program had been planned for decades

这个项目已经被筹划数十年

to ensure the island nation never ran out of clean water.

以确保这个岛国 从不会缺乏干净水源。

And today, as climate change increases the frequency and duration

而在今天，当气候变化 加大了世界各处

of droughts worldwide,

旱灾的频率和持续时间，

more and more regions are facing this problem.

越来越多的地区面临这个问题。

But is it really safe to reuse anything we flush down the toilet?

但重复利用我们冲下 厕所的水真的卫生吗？

To answer this,

为了回答这个问题，

we have to understand exactly what’s inside this cloudy cocktail.

我们必需理解这个 混合物中到底含着什么。

Wastewater is classified into several types,

废水分为几种，

but the primary three are:

其中三大类是：

gray water used in sinks, bathing, and laundry;

洗漱、洗浴和洗衣服的“灰水”；

yellow water containing just urine;

包含尿液的“黄水”，

and black water which has come into contact with feces.

以及接触粪便的“黑水”。

Globally, we generate enough wastewater

全球范围内，我们每天产生

to fill about 400,000 Olympic-sized swimming pools every day.

足以装满 40 万个 奥林匹克游泳池的废水。

In cities and towns with sewage systems,

在带有排水系统的城市与村镇内，

this wastewater combines in underground pipes,

废水在地下排污管道内汇集，

which actually aren’t filled with feces.

其中粪便倒不多。

The average 4,000 liters of sewage

4 千升污水平均

contains only a single liter of solid fecal material.

只含一升的固态排泄物。

But sewage is still rife with dangerous contaminants,

但污水内仍充满着危险的污染物质，

including billions of pathogens and microorganisms,

例如多达十亿的微生物和病原体，

trace chemicals, and excess inorganic nutrients

重金属，以及过量的 无机营养物质，

that can pollute rivers and lakes.

可以污染河流湖泊。

So even if we aren’t planning to drink this concoction,

所以即使我们不打算 饮用这种混合物，

we still need to clean it;

我们仍需要清洁它；

which is why sewer systems typically run to wastewater treatment plants.

这是为什么排水系统通常 接到污水处理厂的原因。

Most plants remove major contaminants

大多数设施从处理的水中

such as feces, pathogens, and excess nitrogen

过滤掉主要的污染物，

from all the water they process.

例如粪便、病原体和过量的氮。

And this involves a ton of biological, chemical, and physical interventions.

这涉及许多生物、 化学和物理技术。

Some of the most important include settling tanks to remove large particles,

其中最为重要的步骤包括 沉淀池中去除大颗粒，

biological reaction tanks where microbes eat unwanted materials,

生物降解池中 多余物质由微生物分解，

and chemical disinfection processes that kill pathogens.

以及化学消毒杀死病原体。

After these procedures, typical treated wastewater in the US

在这些步骤之后， 在美国经处理的废水基本上

is already cleaner than most natural bodies of water,

已经比许多天然水源纯净了，

making it safe to discharge into rivers and lakes.

能够安全地排放至河流湖泊中。

If we plan on reusing the water for non-potable purposes,

如果水源是非饮用的目的，

such as irrigation or washing cars,

像灌溉、洗车，

it gets even further disinfected to prevent bacteria from growing

它会被进一步消毒以 避免细菌在存储中

during storage.

繁殖。

But if we want it clean enough to drink,

但若要使它足够饮用，

there's much more treatment to be done.

还有更多的处理环节。

One common process includes microfiltration,

通常的步骤是微过滤，

where membranes with pores one millionth of a meter across

过滤膜带着直径 一百万分之一米的小洞，

filter out small particles and larger microorganisms.

去除小型颗粒和稍大的微生物。

Next, the water passes through an even finer reverse osmosis membrane,

进一步，水会通过 更精细的反渗透过滤膜，

which can remove particles as small as a tenth of a billionth of a meter.

能够去除小到十亿分之一米的颗粒。

This membrane is semi-permeable, allowing water to pass through,

这个过滤膜是半透性的， 使水分子透过，

but stopping things like salt, viruses, or unwanted chemicals.

但阻止盐类、病毒或 其他化学物质。

After this stage, UV lamps are plunged into the water,

在这一阶段后， 紫外线灯被置入水中，

emitting radiation that permanently damages

发出辐射永久损坏

the genetic material of any lingering life forms.

残留微生物的基因物质。

Sometimes UV disinfection is then combined with further disinfection processes

有时，紫外线消毒 伴随着其他消毒步骤

that use chemicals like hydrogen peroxide

像利用双氧水的化学方法，

to handle a wide range of microorganisms and micropollutants.

可对付多种的微生物和污染物质。

At this point, the treated wastewater is tested rigorously.

到这里，经处理的废水 受到严格测试。

And if it passes, it can safely enter the typical pipeline for drinking water,

一旦通过，它会顺利进入 用于饮用水的管道，

going through the standard treatment procedures

在标准步骤后

before joining the municipal supply.

并入市级的供应系统。

This approach is called direct potable reuse,

这个方法叫做“直接饮用循环”，

but even though it’s perfectly healthy,

但即便它挺健康，

there’s still some concern with such a direct system.

这么直接的系统仍存在着少些问题。

Instead, most places opt for indirect potable reuse,

相反，大多数地区采用 “间接饮用循环”，

where the treated wastewater is discharged to an environmental buffer,

经处理的污水被排放到 外部的储水地点，

such as a reservoir, lake, wetland, or groundwater aquifer.

例如水库、湖泊、湿地 或地下水层。

After some time in this environment,

停留一段时间后，

any lingering chemicals from the treatment process

任何处理过程中残余的化学物质

will diffuse and degrade.

将消散和分解。

Then, the water can be extracted and enter the drinking water pipeline.

那时，水才会进入饮用水管道。

Indirect potable reuse is the process used in Singapore,

“间接饮用循环”是 新加坡采用的方法，

and it's become an increasingly common lifeline for arid regions in the US.

它也在美国的干燥地区 起到愈加重要的作用。

But this system is only feasible in places with centralized sewer systems

不过，这个系统只在存在 中央排水系统

and infrastructure for pumping water into people's homes.

以及居民供水 基础设施的地方可行。

This means it can’t help communities

这意味着它不能造益

dealing with the most serious sanitation issues,

面临严峻卫生问题，

where access to clean water is a daily struggle.

获得纯洁的水很困难的社区。

Researchers are investigating smaller scale technologies to recycle sewage

研究人员在测试小规模设施，

能将污水当场处理成可饮用水。

into potable water on site.

But helping these communities in the long term

但要长期帮助这些社区，

will require us to take a closer look at all the water we’ve been wasting.

我们得认识到自身浪费水的情况。