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In this video Paul Andersen explains how water quality can be degraded by pollutants. Wastewater is the main source of water pollution and can be measure using the BOD (biochemical oxygen demand). Dead zones, cultural eutrophication, disease, and other pollutants are included. A basic description of sewage treatment, septic systems, and water purification is also included.
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Transcript Provided by YouTube:
00:04
Hi. It’s Mr. Andersen and this is AP environmental sciences video 30. It is on water pollution.
00:09
Water pollution made headlines in 1969 when the Cuyahoga River in Ohio started on fire.
00:14
This is that not fire. This is a picture of an earlier fire. In fact the Cuyahoga River
00:18
had started on fire many times going way back into the 1800s. But this caught people’s
00:23
attention, the idea that water could catch fire. It was not the water itself that was
00:27
burning. But it led to regulation to clean up water. And this is the Cuyahoga River today.
00:32
It is cleaned up. The job is not done yet. But water pollution is anything that decreases
00:37
the water quality of lakes, streams, rivers, things like that. And so we categorize water
00:43
pollution depending on where the pollutants are coming from. Point pollution would be
00:47
coming out of one pipe or one ship for example. We can have non point. That is coming from,
00:52
for example, all of the farmer’s fields in an area. And then we can have ground water
00:55
pollution, so it is in that water table, underneath the ground itself. The major pollutant is
01:00
going to be waste water. This is animal and human waste. And so that waste has to be broken
01:07
down. And we generally do that using bacteria. And as the bacteria breakdown the waste they
01:12
require oxygen to do that. And we can measure how polluted that waste water is by looking
01:17
at what is called the biochemical oxygen demand. How much oxygen are these bacteria requiring.
01:24
Now as they do this they pull oxygen out of the surrounding material and can lead to dead
01:29
zones. We see this along a lot of the coasts in the US. We also get an increase in nutrients
01:34
in that area. And so you will get eutrophication. So we get a bloom of algae producers in that
01:40
area. And then also waste water carries disease from one area to another, cholera is a great
01:44
example of that. It is not only waste water that can lead to pollution. We can also have
01:48
chemicals like metals, acids, synthetic materials like pesticides and oil. And then we have
01:53
non-chemical, not at the molecule level. So an example could be garbage that is found,
02:00
sediment that is found or even heat can lead to water pollution. And so we have cleaned
02:04
that up. We have the clean water act. We have the safe drinking water act as well. And so
02:08
how do we clean up that water? Through technology. So we could use a septic system. A municipal
02:14
sewage system. And then we can treat our water as well. And so the categories of water pollution,
02:19
we can have point pollution. This is an example of that. We have sewer coming right out of
02:23
a pipe into a river. We can have non-point source. This could be all the water washing
02:28
over farmer’s fields pulling pesticides and nutrients into the water supply. And then
02:33
we could have ground water pollution. So in this case we have a latrine over here, and
02:37
so the human waste is going to to move down underneath the ground into the water. And
02:42
you can see their well is right here. So you can give contamination like that. And so the
02:46
major pollutant is human waste water or sewage. And so this person is testing the water here.
02:52
What happens is that waste is broken down by bacteria, decomposing bacteria like e.coli.
02:58
But to break it down they require dissolved oxygen, just like you do as you breathe. And
03:02
so we can look at the amount of oxygen that is being consumed and that tells us how much
03:06
waste there is. And so we use a standard called the biochemical oxygen demand. What you do
03:12
is you measure how much oxygen is being produced by these decomposers. Our standard is how
03:17
many milligrams of oxygen, dissolved oxygen per liter is used over 5 days at around room
03:23
temperature, or 20 degrees celsius. And so if we were to take a pristine river, its BOD
03:28
is going to be less than 1 milligram per liter. But if we are looking at a polluted river
03:32
it is going to be a much higher amount. If we look at sewage, treated sewage, it is going
03:37
to be 20 milligrams per liter. But if we look at raw sewage in the US it is around 200.
03:42
And if we look at it in Europe it is going to be around 600. Now you may think why do
03:46
they have more polluted sewage? It does not have anything to do with the waste. It is
03:50
that in the US we produce so much water. We take so many long showers, flush the toilet.
03:56
And so as we do that we are diluting these BOD numbers. Now it also lead to increases
04:00
in nutrients and eutrophication. So this is pollution leading to an algae bloom. We have
04:05
a bunch of blue-green algae that are using the nutrients in it and so you are getting
04:09
a huge explosion of growth. You might think this is a good thing. But what happens, this
04:13
is an algae bloom off the coast of California, and so as you get an algae bloom like this,
04:18
there are a bunch of producers, algae in that area. But then they eventually die. And as
04:23
they die these same decomposers are going to break it down. And as they do that they
04:27
pull oxygen out of the water. And so we are producing what are called dead zones. This
04:31
is a massive dead zone, around the size of Rhode Island in the Gulf of Mexico. And what
04:36
we are doing is pulling the oxygen out of the water. And so fish are dying. Shellfish
04:40
are dying. And you can see that we have dead zone all around our planet. But it is going
04:44
to be aggregated in areas where the water is moving out into the ocean with huge amounts
04:49
of nutrients. So we have this eutrophication and then these dead zones are being created.
04:53
Also in that polluted water we have disease. And so in India you can see here that they
04:58
are washing themselves in the water. But we also have waste water in there as well. And
05:02
sometimes we are pulling the drinking water out of there and so it can lead to disease.
05:07
Cholera outbreaks in India or in South America are awful but it is a bacteria that is moving
05:12
into the waste water and then we are drinking it back in. And so there are so many diseases
05:16
that can be found in water. And so scientists use an indicator species, like e.coli or fecal
05:21
chloroform numbers. And we can see if that is found in the water then we are going to
05:25
find other diseases there as well. Now aside from waste water we can have chemical pollutants.
05:29
This is a big ash spill and we are moving a lot of chemicals into the water itself like
05:34
lead, arsenic and mercury. Generally these things are going to be found underneath the
05:38
earth, but with mining we are moving them up and they are getting into the water. We
05:42
also have that same problem with acids. So acid mine drainage is being released but it
05:47
used to be trapped underneath the earth. We also have synthetics that we are producing
05:52
like pesticides. And then finally oil. We are pumping it underneath the earth, but now
05:55
it can contaminate with any kind of an oil spill. We can also have non-chemical pollutants.
06:00
And so this is a pretty sad picture. This is an albatross chick and its mother and father
06:05
were feeding it debris, marine debris. They just thought is was food. And eventually the
06:10
chicks are dying as a result of that. But it can also be sediment, dirt. So this is
06:14
a construction zone and a lot of that dissolved sediment is moving into the water supply.
06:19
And then finally it can be heat. And so at this power plant, as a result of that combustion
06:24
we are moving a lot of that heat and that is impacting the environment as well. And
06:29
so we have been regulating this since the 1970s. And so the most famous one is the clean
06:33
water act. But we also have the safe water drinking act. And what they do is they put
06:38
regulations on the amount of pollutants that can be moved into the water supply. Standards
06:43
as far as water pollution. So how do we clean it up? We can use something like a septic
06:47
system to treat our sewage. So the sewage moves in here. Then you will get a lot of
06:51
the sediments settle out. And the scum will be on the surface. And then what you have
06:56
is bacteria this whole way that are working on it. And so they are moving it out into
07:00
a drain field. And the bacteria and breaking that down. Now the problem is if some of it
07:05
gets out of the septic system, or the septic system fills up, we can get leaching. It moves
07:10
down into the ground water. This is a sewage treatment plant in Europe. And so the parts
07:14
of sewage treatment are pretty simple. First of all you will get pretreatment where we
07:18
are removing things like big bits of garbage out of it and we are treating it with a little
07:22
bit of oxygen. But then generally you have a primary treatment. And so in this case what
07:26
you are doing is you are letting a lot of that sediment settle out. And that is going
07:30
to take one pathway where we digest it further, dry it out. And lots of times it moves to
07:34
a land fill. But then we have these big tanks where we are aerating it. And so what you
07:38
are doing is bubbling oxygen into it so these decomposing bacteria can breakdown that waste.
07:44
And eventually it is going to move into the water supply, maybe back out into a river
07:48
once we hit the right BOD level. After it comes into the river then somebody downstream
07:55
is going to have to treat that water. So we also have water purification. In that we are
07:59
going to have big filters. We are also going to treat it chemically. We will treat it with
08:03
chlorine for example. But the big problem with this is that we are removing the water
08:09
upstream and dropping sewer downstream but then there is going to be another city just
08:13
down the way. And so did you learn the following? Could you pause the video at this point and
08:17
fill in the blanks? Let me do it for you. Water pollution decreases water quality. It
08:21
could be point, non-point, or groundwater contamination. The pollutants, the major one
08:27
is going to be the waste water. We can measure that using the BOD. But is can lead to dead
08:31
zones and also cultural eutrophication, these explosions of algae. And we also have chemicals
08:37
like metals, acids, synthetics that we produce, and oil. We have solid waste, sediment and
08:41
then remember thermal pollution. How do we clean it up? Through regulation and technology,
08:46
septic systems, water purification and then sewage treatment. So that is water pollution.
08:50
It is awful, but I hope that was helpful.
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This post was previously published on YouTube.