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