大家好 感谢收看今天的Dnews Plus
Hey everyone, thanks for tuning in to Dnews Plus again today.
I am Trace.
And this is episode three of four on drinking water.
So far we’ve talked about when drinking water became a thing.
We’ve talked about some of the first technology
that we’ve used to get drinking water to us.
Regulations in drinking water.
What is in your drinking water,
which I think it won’t bring us to today,
because we talked a little bit about fluoride.
I feel like you know a little bit about fluoride, right?
Today we have a special guest in
to talk about water defluoridation.
It is Katya Cherukumilli,
a PhD candidate in environmental engineering at UC Berkeley.
– 欢迎 最近怎么样- 谢谢 非常不错
-Welcome. How’s it going?-Thank you. It’s going great.
Later we’re also gonna talk about
if we have run out of the availability of drinking water
and all sorts of other stuff.
So let’s kick into this.
So, how did you get interested in studying drinking water?
I became interested in this topic,
because I believe that
everyone has a fundamental human right to clean drinking water,
that should be fulfilled.
And currently, this basic need is not being met
for over 780 million people.
Also I was born in India,
and when I moved to the US,
I noticed the stark contrast
between the access to clean drinking water that people had.
And I learned quickly during high school
and college through my studies,
that this field of drinking water
really encompasses and combines my interests in
environmental science, natural resources and global poverty.
So when you look at drinking water,
because of the way you’ve been studying in over the years,
I imagine you see certain impurities in there, right?
So what’s the big one that you study?
I focus on an inorganic contaminants that naturally occured called fluoride.
Got it. I think some people have maybe heard of that
out there in the world,
cause we do put that in our drinking water
here in the United States.
But it naturally occurs you say,
does it occur naturally in the United States as well?
In a few states, such as Oklahoma and Texas,
you have high concentrations of fluoride in groundwater,
naturally occurring as a result of
fluoride leaching out of rocks.
It’s embedded in some minerals in rocks and aquifers.
And that’s why it equilibrates at such high concentrations.
Got it. And what about the rest of the world?
Does it… There are areas where it’s worse?
So almost 200 million people around the world
are consuming fluoride contaminated groundwater
as their primary source of drinking water.
And some of the areas that fluoride naturally occurs
as a result of this geo-genic contamination,
include northern plains of China,
印度的许多州 东非大裂谷 墨西哥中部
many states in India, the East African Rift Valley, central Mexico,
and Argentina and the Middle East.
哇喔 我觉得 这些地区的这么多人
Wow, yeah, I mean that’s a lot of humanity,
it seems like that have to drink this water.
So what happens when they do that,
if they’re consuming fluoride at high concentrations?
What does that do to your body?
So, some of the effects that people have already noted
that medical professionals include dental fluorosis,
which you can start developing
if you’re a child under 8 years old,
when your permanent teeth are still forming.
This is basically a modeling of your teeth enamel.
You can also develop irreversible crippling skeletal fluorosis,
which basically deforms you,
and makes it unable for you to go to school or work,
or have a normal life and family.
And other side effects include
fluorides effect on the intestinal villi.
So it inhibits your ability to uptake nutrients,
so you could develop anemia or lower IQ.
And recently fluoride was actually classified as a neurotoxin.
So why the hell do we put it in our water then?
So as I mentioned earlier
in low concentrations and in moderation as with many things
fluoride can be good for you.
And so we add about 0.8 to 1 parts per million,
and the World Health Organization and the US EPA limit for fluoride
is around 1.5 parts per million.
OK. So like with anything in this area,
it’s about dosage more than it’s about presence.
Exactly. The amount which you intake
for how long you can take it,
and in what forms really impacts the outcome.
嗯 明白 明白
OK. Got it. Got it.
When it comes to fluoride,
how is it that it can be good for you then?
If even at low doses, if it high doses,
can be a neurotoxin potentially
and cause all of these problems..
How about low doses? How does it help?
Yeah, that’s a great question.
So for the last 70 years,
people in the US have been…
municipalities have been adding it to our drinking water.
And so this started in 1940s,
because they found a beneficial correlation
between a reduction in the incidence of dental caries and cavities,
and tooth decay through the addition of
fluoride in drinking water in low quantities.
And basically what happens is
your enamel and your teeth are made up of hydroxyapatite.
And when you intake fluoride,
this forms a acid resistant layer on your teeth called fluoro apatite,
by allows for the prevention of cavities.
Hmm, so it’s actually like working with your body.
– 对的- 哦
And that’s all just from fluoride which,
as you said, naturally occurs.
So where does the fluoride come from?
In many parts of the world,
the underground aquifers contain certain rocks,
which have fluoride minerals that leach out over time,
and equilibria very high concentrations in the groundwater.
So you end up taking this water out of the ground,
and you wanna, you know, put in a cup and have some.
But if you do that ,
– 你就会摄入过量的氟化物- 对的
-You’re gonna end up drinking too much fluoride.- Exactly.
And then you could end up with a lower IQ or crippled,
and number of other problems,
– 感觉很可怕- 是的
-Sounds awful.-It is.
And so how does it cause those things to happen to you?
You know what is it about the fluoride
that is giving so many problems.
– 因为我不是医学专业的- 当然
-So not being a medical professional.-Sure.
I can’t answer that question in great detail.
But I do know some theories that are out there,
such as the formation of fluoride.
Calcium fluoride precipitates on your bones,
or leaching out calcium,
those are two different methods.
OK, that doesn’t sound good either.
How is it that we get this fluoride out
before, of course, then we put it back in, I guess.
Well, the areas in the world
where we’re actually fluoridating our water,
or adding fluoride to our water,
don’t really have naturally occurring fluoride concentrations.
So most groundwater, for example in the US,
doesn’t really have excess or naturally occurring fluoride.
So that’s why our municipalities
for the last 70 years have been adding fluoride to our drinking water.
现在在这些地区 比如 嗯 中国
Now in areas such as, uh, China,
the Northern Plains of China,
the East African Rift Valley,
many many states in India,
呃 阿根廷中部 墨西哥北部 中东地区
uh, central Argentina, northern Mexico, the Middle East,
fluoride is naturally occurring at extremely high concentrations.
So in areas like this,
there’s a variety of technologies already present for removal fluoride.
But a lot of them are not locally available or locally affordable,
so that’s why I’m focused on designing an ultra low cost technology.
OK, so can you tell us a bit about what you’re designing?
– 可以透露吗- 可以的
-Is that allowed?-Sure.
So one thing that I’m focused on,
is providing an alternative to activated alumina filters.
– 好的- 那么目前世界上很多人
-OK.-So currently many people around the world
especially in middle-class consumers,
they use activated alumina filters to remove fluoride.
And this material, activate alumina,
and all aluminum metal actually comes from an Oracle bauxite,
which is found in many countries around the world.
There’s large deposits in Australia,
还有印度 加纳 几内亚
India, Ghana, Guinea.
And the reason I chose to focus on bauxite is because
it has a strong affinity for fluoride first of all.
And it would be a relatively simple and easy to maintain system,
that is less complex than something
such as reverse osmosis,
which requires a lot of skilled labour to operate and maintain.
好的 可能大家不了解 反渗透到底是什么呢
OK, so reverse osmosis just to remind people is what exactly ?
It’s a pressure driven membrane system,
which requires you to have very skilled labour to operate.
– 是的- 它会造成 它会产生许多废水
-Yeah.-And it caught, it creates a lot of waste brine.
And it’s also very inefficient
in the sense that you waste a lot,
lot of water that you’re trying to treat.
Right, so you end up running this water through a membrane,
and adding all of these different things to it
to try and pull the fluoride out.
And then you end up with a waste product,
but you also get clean water.
– 差不多- 好吧 差不多 我还是描述得差不多嘛
-Sort of.-OK, sort of. I was sort of there.
But and then in your method what exactly,
how does the bauxite help remove the fluoride?
Like it they attract each other
and then you can kind of filter it out? Or…
So bauxite has an active mineral in it called gibbsite,
which is an aluminum hydroxide
And that’s actually what you’re trying to purify and leach out
when you’re making the more refined and more expensive activated the aluminum material.
And gibbsite, uh, co-occurs with other mineral oxides present in bauxite,
such as iron oxides, silicon oxide and titanium oxides.
My argument is that
we don’t need to apply very chemical or thermal intensive methods
to leech out the impurities present in bauxite.
And we can in fact use it
in addition to all the things that exist with it.
Mm-hmm, and then what … how does it …
what is the fluoride do when it comes in contact with that?
So the idea of this process is
we’re crushing the bauxite to very fine particles high surface area.
And we would apply it in a batch process,
where the fluoride can adsorb onto it,
meaning that it’s coming out of the aqueous phase,
and attaching on to the solid particles.
喔 很棒 那随后只需过滤出那些粒子
Oh, cool. And then so then you just filter those particles out.
And you have a cleaner water,
or at least a defluorided, defluorided.
– 去氟化- 去氟化
– 这词挺难的- 是有点难念
-It’s a tough word. -It is a weird word.
So the idea of post-treatment methods,
you could use membranes,
you could use slow sand filters, rapid sand filters.
There’s a variety of options
– 沉淀 沉淀池 混凝剂- 是的 但这样来看
-Settle, settling tanks and coagulant.-Yeah, but at that point …
the dangerous thing of the fluoride at least is, has been removed.
Yes, it’s been partitioned on to something
which you will then remove.
And what do you do with the fluoride after that?
So then the idea.
– 显然还停留在理论阶段- 是的
-This is obviously still in the theoretical phase.-Sure.
Because I’m … I’ve only been working on it for a few years.
But the idea would be potentially to
retrieve value from the bauxite
by selling it back to alumina manufacturing plants,
or perhaps even regenerating it
by doing a caustic base wash.
Mm-hmm, and so then you would what remove the fluoride,
and be able to separate that out from the bauxite,
– 然后再利用这些铝矾土- 确实可行
-and reuse the bauxite?-Potentially.
– 但是最好还是- 哇喔
-But ideally it would be great,-Wow.
– 将它卖回给铝厂- 是的
-if we could sell it back to the aluminum manufacturers.-Right.
because small flora, amounts of fluoride in parts per million
shouldn’t affect their process for producing aluminum from it.
It reminds me a lot of a series we just did on recycling,
where we’re talking about taking plastic
you cut it up, you melt it down
and then you resell it back to people
who can then use it for stuff,
because it doesn’t matter that it’s not
as pure as fresh plastic to some manufacturers.
So if you don’t know that series,
you can go back and watch is pretty fun.
But anyway, yeah, so it sounds a lot like that
which is already been a proven business model,
so kind of neat.
I guess we’ve already covered a lot of this,but
what about some of the other technologies that
that people are using to remove fluoride.
Like you say … We don’t have it here in the United States,
so we put in a very small amount of it.
But what about places that
may not have access to the system that you’re working with?
What other systems are people using now?
Yeah, that’s a great question.
不过 我先澄清一点 在美国部分地区
So quickly for one point of clarification in the US,
there is some naturally occurring fluoride
in Oklahoma, parts of Texas.
But luckily, the people living there have access to
municipal piped water supply.
And this is not the case in
rural India or rural Africa.
There are many many other places
where people are reliant only on bore wells,
or groundwater wells for their main source of drinking water.
And so that’s why we don’t really see fluoride as a huge epidemic,
or fluorosis as a huge epidemic here in the US.
But it could be if we didn’t have those municipal …
– 多亏有了市政供水系统- 是的 如果我们没有……
-Power turn, municipal system.-Exactly. We didn’t have conti…
If we didn’t have continuous water supply,
we could also face similar problems.
Wow, we’re just two steps from chaos.
We’re definitely lucky and privileged to be living here.
So back to your question about existing technology.
So we talked a little bit about reverse osmosis,
a little bit about activated alumina filters.
Some additional technologies that I looked into
when I first started this research,
were aluminum electrocoagulation?
which basically uses aluminium metal plates and a power supply
to generate the aluminum hydroxides,
which I mention are already found in bauxite.
So the idea there would be to,
basically have a power supply,
and oxidize the aluminum plates
into something that could create an absorbent for fluoride removal.
Another option that I’ve seen
in Nakuru Kenya is bone char.
So they’re taking massive amounts of bones,
and charring them by putting them in a huge furnace,
and using that extremely porous high surface area material to remove fluoride.
I kind of like traps it, or
– 像机油滤清器或类似的东西吗- 有点类似 可以说是
-Like oil filter or something like that?-Just similar, I would say,
– 相似的吸附过程- 好的
-It’s a similar absorptive process.-OK.
You just brought up a great point that
activated alumina can be compared to Brita filters,
which contain activated carbon.
Right, OK, cool.
So that’s a kind of way to think about it in your brain,
is that like when you say activated alumina it,
for people that aren’t necessarily familiar with that
think of the filter on their water faucet,
kind of pitcher, right?
If that’s removing some impurities,
this is just removing very specific ones like fluoride.
Exactly, because fluoride has a specific affinity for aluminum.
that actually brings up a really good point,
if you can imagine how much effort,
and time and money it takes
– 来妥善保养你的碧然德过滤器- 是的
-to properly maintain your Brita filter at home,-Yeah.
you can then understand
why we are thinking of a community scale
water treatment system with bauxite.
Because we can’t expect people
that are living in these rural remote regions that,
that are very impoverished
to have an additional burden
to take care of their own water.
So that’s why I’m not in favor of a household treatment system
with this bauxite technology,
and I think it’s better off as a community scale.
Right, yeah, and I’m sure on top of that
just to kind of riff off of your point is
for us we have this kind of waste system where I can,
you can bring me a tiny thing that I can put in my house,
and then I can give it to somebody else
who takes it and disposes of it properly,
and that’s also more difficult
in places that don’t have that kind of infrastructures.
So much, it’d probably be a benefit to have it on a community scale
– 更有利些- 对的
-in that respect as well.-Exactly.
Yeah, because it’s more it’s easily maintainable.
So when it comes to stuff other impurities like arsenic,
where do those come from?
Is it also from rocks underground?
或者…… 这么问 为什么
Or… And if that’s the case,
why isn’t all water filled with all of these weird little things
that you never think about?
So it is very much a geographical problem.
So you can find maps that show you exactly
where there’s rocks and soils
that contain high levels of arsenic.
And a big area of the world,
where this is a problem is in West Bengal and Bangladesh.
My lab is also focused on arsenic remediation technologies.
Our labs is known as ECAR,
Electrochemical Arsenic Remediation.
哦 哇喔 好吧 那么
Oh, wow. OK, and so,
other than arsenic and fluoride,
I’m sure they’re removing things that
you know maybe aren’t as dangerous,
or is it all like your lab maybe not.
But when somebody wants to take water out of the ground,
are there other things that I have to worry about?
That might be in that water I mean,
obviously pathogens and things,
but I mean in terms of mineral content.
Umm, those two are probably the biggest right now,
that are in the forefront of
people trying to figure out low-cost and affordable technologies for.
But if you look at Salinas in the Central Valley in California,
people are very worried about nitrate,
coming from agricultural effluent,
and also worried about arsenic.
So nitrate is very much a problem here.
Selenium is an up-and-coming emerging pollutant.
So it seems like adding a little bit of fluoride is OK,
but removing it is even more important.
So it’s pretty awesome that you’re doing what you’re doing.
Thank you so much for joining us today
and talking to us about this super awesome stuff.
And we want to also take a moment
to thank our partner for this series.
The Blum Center for developing economies.
There are an innovation and research hub
that is tackling issues in global poverty,
and they’re pretty amazing.
So make sure you check them out.
You can find them over on the web
at berkeley.edu, Blum Center.
You can also find Katya on Twitter, right?
You just joined.
katyac_h2o. So go give her a quick follow.
Guys you can also find me on Twitter @tracedominguez
You can find the show @dnews.
Give us a tweet with the hashtag Dnews Plus,
if you want to ask us any questions about this,
or any other episode that we’ve had in this series.
Let us know down in the comments,
If you feel differently about water fluoridation or defluoridation now.
And thanks so much for tuning in to Dnews Plus.
大家好 感谢收看今天的Dnews Plus