This time, we reveal the relentless struggle
to keep water flowing to our cities.
One of these pops can fill up
an Olympic sized swimming pool in 20 seconds.
The hidden army working to keep our water safe.
You've got a less than 15 minutes lifespan
once you enter into this water.
And the future of our water waste.
People flush their toilet
and it turns into fuel for cars and buses.
Half the world's population
live in urban areas and the number is rising every second.
Each day is a race against time
to house, feed, water and move more than 3.5 billion people.
It's an impossible daily challenge.
The slightest glitch can bring a city to its knees
and every 24 hours, it has to be done all over again.
This is the story of how cities work.
(upbeat music)
For centuries, cities have been built
near a fresh water supply.
Without it, we'd be lucky to live three days.
But this most basic human need can be deadly too.
Get the supply wrong and it can poison us.
Get too close and it can drown us.
Water,
we need it and must respect it.
With every passing year,
the challenge of providing water to billions of people
becomes harder and harder.
Nowhere is this more apparent than the city of Los Angeles.
(dramatic music)
This is the key to LA survival.
The Hoover Dam on the mighty Colorado River.
It is a whole state away,
but the reservoir it controls, Lake Mead,
is a critical supplier of drinking water to the city.
The route to LA runs 250 kilometers
downstream to the Colorado river aqueduct.
Greg Hare is one of the pilots charged
by the authorities in Southern California
with keeping this precious structure safe.
When I'm doing security patrols,
I'm mainly looking for people
who aren't supposed to be there.
If I see something that I believe is suspicious,
I will call our dispatch office and have them
take the appropriate action.
(tension music)
This manmade aqueduct
provides Los Angeles and Southern California
with approximately 4 billion liters of water a day.
Because of its importance to the state,
surveillance was heightened after the 9/11 attacks.
Our special security patrols
are tied to whatever the terrorist alert level is.
But it's a huge challenge.
The Colorado river aqueduct is a 389 kilometer network
of tunnels, canals and pumping plants.
It's sheer size makes it virtually impossible
to protect efficiently from the ground.
We patrol the aqueduct with the airplane
from the air.
The reason we do that
is because we can cover the entire length of the aqueduct.
But Greg's aerial patrol
allows him to police the remotest points
of the aqueducts route where few ground patrols
are able to reach.
Desolate areas where people aren't around to watch it,
you could have something going on out there
that you wouldn't know about unless you could fly out there
and take a look at it real quick.
People aren't the only threat.
Greg and his team run constant checks
to scan the waterway for signs of damage.
(suspenseful music)
The aqueduct must carry the city's water
across no less than three hostile mountain ranges.
In the 70 years since it was built,
the population of California has risen by more than 500%.
The aqueduct is a backbone of our water supply system.
It's been the most reliable
delivery of water for the last 70 years
for Southern California.
The challenge was to get water from the Colorado river,
some 242 miles, into Southern California
over several mountain ranges in a very dry and hot desert.
Don Nash oversees all five pumping stations
along the aqueduct, including the Julian Hind's Plant.
We're at Hind's Pump Plant.
This is the last lift on the Colorado River aqueduct.
It's taken about 25 hours for the water to get here
from the Colorado River.
This station is the last and most powerful
of the pumping stations.
Each day, it must defy gravity
to lift over 4 million tons of water
over 130 meters to the top of Eagle mountain.
And this is the last 441 feet it takes
to overcome the last mountain range
to get us into Southern California.
The power needed
to lift the water is staggering.
There's one pump of nine that we have here.
One of these pumps can fill up an Olympic sized swimming
pool in 20 seconds.
It's actually discharging right here underneath our feet
and going up the hill some 441 feet to the top of the hill.
Don's 912,500 horsepower pumps
lift water over the mountains,
but there's another natural threat
waiting just on the other side.
(tense music)
This is Lake Mathews,
the final reservoir on the Colorado River aqueduct
where the city's water is stored
before flowing into LA for treatment.
Storing vast quantities of water in the middle of the desert
produces unexpected challenges.
The lake is a breeding ground for tiny intruders.
The advantage of having water in a lake
is that you can store it.
The disadvantage is that now it's a large enough reservoir
that is going to behave as a lake.
Dr. Rick DeLeon and his team of divers
are fighting an ongoing battle
against the mighty army of small,
but persistent quagga mussels.
These mussels can actually grow to very high densities.
100,000 per square meter is not uncommon.
They have been documented to grow up to 700,000
per square meter.
The mussels have no direct effect
on the quality of the water,
but if left unmonitored,
they could block supply pipes to the city
with potentially devastating consequences.
And when the mussels colonize,
they can actually close that space
and not allow much water to go through
and put a strain on the pumps.
So they need to be removed
to allow the water to go through uninterrupted.
(suspenseful music)
Dr. DeLeon and his team
place test plates in the lake to monitor
the mussels growth rates.
Today, divers Steve and Kelly,
are retrieving one that's three months old.
(tense music)
Steve and Kelly, are the quaggas growing just on
just rocks or are they also growing on the silt?
Just on the,
just on the rocks at this point.
I think (indistinct).
After a 30 minute dive,
Steve rises to the surface with the test plate.
It is completely covered in quagga mussels.
That's surprising how
much they're still growing in there.
What depth was this?
This was 53 feet. -: 53.
So deeper than we thought.
The test plate reveals
a steady increase in the number of quaggas.
One of the reasons why we monitor is to see
is there frequency of which they need to go in there
and clean up.
For Dr. DeLeon,
this means that not long from now
a full-scale unblocking operation will be needed
to keep water flowing to Los Angeles.
For us, it's really a matter of control over time
to reduce the impact that it can have on us
and prevent them from interfering
with our normal operations.
Humans cannot survive without a constant supply
of drinking water.
In the next 20 years,
our cities will grow to such a point
that demand will outstrip supply
from rivers and lakes by 40%.
For cities like Barcelona,
that means a constant battle against drought.
The impact is already being felt by Aigues de Llobregat,
one of the city's main drinking water suppliers.
We have not enough water to supply all these people.
In the last five years,
Barcelona has turned to a radical new source
that could solve supply problems forever,
seawater.
But seawater has a higher salt content
than the human body can process.
Drinking large quantities could result in death.
In 2009, the city built the biggest desalination plant
of its kind in Europe on Catalonia's shoreline.
Overseen by plant director,
Carlos Miguel Centeno.
(Carlos speaks in a foreign language)
This brightly colored super hub of pipes and pressure pumps
is equipped to bring an average of 200 million liters
of sea water into the plant a day.
To make it drinkable,
it's killer salt content needs to be removed.
This desalination happens
through a process called reverse osmosis
and takes place inside these blue tubes.
Seawater is pumped through a coiled membrane
fine enough to filter out the salt molecules in the water.
It allows pure water
to flow through to the next stage of its treatment.
And just minutes into the day shift,
engineers have found a problem with a pressure pump.
Carlos Miguel must act fast.
A faulty pump could seriously impact
Barcelona's water supply.
(Carlos speaks in a foreign language)
Seawater can't keep flowing in
during the membrane change
so the control room shuts down a section of the plant.
This is not good news for Carlos Miguel
as less water is now available to the city.
Changing membranes is no easy task.
These seven heavy cylinders
must be perfectly placed in their tube
for their power and pressure connectors to work.
The team add a coat of glycerin
to ensure they slide in smoothly,
and apply some heavyweight muscle.
Once the tube is tightly sealed,
the pump can startup again,
bringing supply back to full capacity.
Pumping seawater through an army of over 17,000 membranes
is not enough to guarantee a safe drinking supply.
The city's water must go through several purification stages
before it's fit for consumption.
And it's here in the plant's laboratory
where critical testing takes place
before releasing drinking water into the city.
(Carlos speaks in a foreign language)
Biochemist Maria (indistinct)
leads a team of scientists
whose job it is to test samples
from every step of the process.
After its journey from the sea and a battle against time,
this water is now safe for the city to drink.
Desalination is important for Barcelona
because with this new supply of water,
we have 20% of the water that Barcelona needs.
Barcelona's use of the sea
could be at the forefront of a water revolution,
a way to guarantee future supply
for the world's growing city populations.
(suspenseful music)
Cities don't just depend on water for drinking.
Waterways provide a vital transport link for moving goods
in and out of our cities.
London Gateway.
Today engineers are taking delivery of a fleet of cranes
among the biggest in the world.
They're approaching British shores
after a six week journey from Shanghai.
This marks a turning point for London.
These key cranes are capable of unloading
some of the largest cargo ships in the world
at unprecedented speed.
Engineer, Russ Broughton is supervising the unloading.
It's a really big day
in the life of London's nearest port.
Yeah, we're all very excited about it here.
The UK is an island nation
and 90% of our goods come in by sea
and it's nothing new to have our ports in London.
It's what the Romans first did 2000 years ago.
It may be the same waterway
but London is now a capital city
with millions of inhabitants.
The key point is that this is the biggest consumer market
in the UK.
This is Europe's largest economic area.
So we're once again,
gonna bring the biggest ships in the world
to the biggest point of consumption in the UK.
To do that, we need some big pieces of kit.
Each crane is 138 meters tall,
taller than the London Eye.
It's the culmination of years of planning
and millions of pounds spent,
but Russ and his team are worried.
There's no crane in the world
big enough to lift each 2000 ton steel structure
onto dry land.
The only way to unload them
is by dragging them off the ship.
This can only happen at high tide
when the deck is level with the quayside.
The tide is flowing pretty quick at the moment.
Then we've got one hour
to get this crane back onto the land.
It's 2000 ton, we're on a moving vessel
and if we don't do it in that hour
then we ended up with 2000 ton of metal
sticking out at the Thames
and I'm not sure how we're going to get that out.
The ebb and flow of the Thames tide
can change water levels by a massive seven meters.
Russ and the team only have one shot to get it right.
To roll the crane off the ship,
engineers must lay down
four industrial sized bridging tracks.
The vessel and the dock must be perfectly aligned
for the crane to slide off.
The tracks must be fitted in a matter of minutes,
but the team can't begin to put them into position
until the ship and the quayside are almost level.
This is it now.
This is the last couple of minutes
to just put the final bridge in to position.
Any second now, this crane's gonna start rolling off.
The rails are aligned,
but the worst is not over.
Yeah, this is it.
the ropes are all gone tight now
and you can see the crane starting to move.
This is the bit that we've all been waiting for
and it's do or die.
They must make this work or risk costly delay.
We're now at high tide.
We've got about 45 minutes to an hour
to get this off safely onto the land.
There's another complication Russ can't control.
So he relies on engineers aboard the vessel.
As the crane is unloaded,
its weight threatens to destabilize the ship.
To keep it level,
engineers must pump thousands of liters of water
into the ballast tanks on the other side of the ship.
If they get it wrong,
the crane could slide off the ship and into the Thames.
On the quayside,
engineers have wired in a network of winches, pulleys
and wire ropes.
This choreography of slow but meticulous pushing and pulling
begins working in combination to control
every move of this giant structure.
A sudden movement or level change in the water
could spell disaster.
(suspenseful music)
It's taken over 40 minutes of coaxing,
but finally the crane makes it onto dry land.
The final bit is just to get an inch perfect
so when we lower it down,
then I want to see it lands centrally on the rails.
British and Chinese engineering teams
have completed this mission.
And the construction of London's newest port
is a step closer to realization.
Thankfully, there were no problems on this one
and it all went very smoothly.
Very happy here.
Sweet, isn't it?
You never know but it all went very well.
Waterways may serve to expand our cities,
but rivers can be treacherous pathways for city dwellers.
Hundreds of boats carrying thousands of passengers
use the Thames every day.
Most journeys go off without incident
but the river can be a dangerous place.
There's many hazards on the Thames,
mainly the tide and the traffic.
So other the vessels going up and down
and the weight and tide,
more barges and boats and bridge piers.
This is a difficult environment
for the rescue workers who police it.
Last year, the emergency services
were called out over 850 times,
making this the busiest stretch of water
in the country for rescuers.
It's the job of the Royal National Lifeboat Institution,
a charity operating along the coast of the British Isles
to act as the river's first responders.
Helmsman Stantod has served almost a thousand hours
for the team.
The Thames can be quite a ruthless beast.
The currents and the coldness of the water
coming down from the mountains.
It makes it a very hostile place.
This gives rescue services
little or no time to save a casualty once they fall
into the Thames.
You've got less than 15 minutes lifespan
once you enter into this water.
(tension music)
RNLI Tower Station base
is one of four on the Thames
set up in the wake of the 1989 Marchioness disaster
which claimed 51 lives.
Since then, the RNLI has rescued almost 3000 people
from the Thames.
For volunteer John Mullen,
there's no other service completely committed to saving
lives on the river.
The river is a problem
for the standard emergency services.
So the RNLI presence here gives a committed rescue service.
No other job, just to go out and help people
that need the help here and there.
The single biggest challenge probably
is trying to prepare for an event
that you don't quite know how it's gonna pan out.
We've been to people that's been having babies,
we've been to fires,
we've been to people are stranded in the mud.
It could be anything.
That's part of the appeal of this job.
(bell ringing)
Right now, the London coast guard
has issued an emergency call.
The RNLI crew has 90 seconds to get on the water.
On duty is helmsmen Michael Neild,
and crew members Colin McCarthy and Giles Harrison.
(suspenseful music)
A suspected incident at Westminster Bridge
has put all the capital's rescue services on high alert.
Police, fire and ambulances are on their way.
(indistinct) on the sea.
But even more testing
is the absence of information they're given.
The information that comes through to the coast guard
is, you know, usually done in a panic.
It's not by any means the exact picture
of what you're gonna get when you get there.
(indistinct)
We got a report of a male who threatened to jump
the Westminster Bridge.
(indistinct) at this moment are able,
with surrounding cameras, to look on the bridge.
If a person falls into the Thames,
he or she only has minutes to live
in water that's 10 to 15 degrees Celsius.
After that, a fearsome undercurrent,
and the chances of drowning are high.
It's not clear whether anyone actually went into the water,
but the emergency services
have to take every report seriously.
Crew members Michael, Colin and Giles
search every meter of the river.
The London Tower, we've searched both sides of the bridge.
We've got nothing obvious.
Fits your description if you don't have him.
Five foot seven and medium build. Over.
London Tower. Yeah, that was all received.
Now an obvious-
Helmsman Michael Neild needs to stay alert.
Powerful currents surround the bridges foundations
could easily suck their vessel into its walls.
Nice. He's on his phone I think.
Leaning on the side.
There's no further information
to suggest anyone did go into the water.
It's starting to get dark.
If there was anyone in the river,
fast moving currents would have carried them far downstream.
Eventually, the search is called off.
Just no trace basically.
Let's hope police have tried all avenues
and got to a point where they decided that's it.
There's no point in issuing anymore.
(dramatic music)
The team head back to their base.
It's not a question of if,
but when the next call will come in.
And for these young unsung heroes,
the battle on the Thames continues.
I'm not sure I'd really wanna work anywhere else.
There's always something going on here
which is a nice thing.
That's what I enjoy the most.
Water can be our worst enemy,
but it can also save our lives.
It protects us from the most devastating
of everyday disasters.
Fire.
In 2011, the US fire department received reports
of structural fires every 65 seconds.
We save lives
and there is nothing more that you can do
that's more gratifying than to save a life.
In New York, there are almost 20,000 people
per square kilometer that depend on the fire department's
protection at all times.
The entire force is helpless without fast access
to massive amounts of high pressured water.
This city solution is a network of 110,000 fire hydrants
visible on every city street.
They connect the city's water mains directly
with the fireman's hose.
For firefighter Michael Gallo,
hydrants are critical in the fight against fire.
Fire hydrants in the city of New York
are of paramount importance.
We rely on them.
It doesn't matter how good my rig is
or how fast they get there,
without water we don't put fires out.
(dramatic music)
6:00 a.m.
One of the city's vital hydrants
has been knocked down by a car.
The Department of Environmental Protection
is dispatching a replacement.
A broken hydrant could mean the difference
between life and death.
John Castiglioni and his team have just two hours
to fit the replacement.
But some hydrants in the city date back over 50 years.
This is the lead from back in the day.
As you see, it's soft.
This was around the joint,
and here's today's technology.
See the comparisons.
This rubber gasket stays in the retaining plan.
Back in the day they didn't have that technology.
The hydrant went in around the pipe
and they used to make up the difference of space
with the leg.
Now today's technology, you're using a rubber gasket,
the retaining gland,
and the bolt.
They go in.
It holds everything in place.
(dramatic music)
As the work starts,
there's an unusual amount of water coming out
of the mains pipe,
making the attachment of the hydrants
retaining gland an impossible task.
The team bring in a high powered suction hose
to rid the area of excess water.
For now we're gonna install the hydrant.
Right on the hydrate branch,
we're gonna fold it together to block it off,
find the bolts up,
lock up the back
and then we're gonna all come to the hydrant gate.
It makes you to hide your work properly.
It's a tried and tested plan.
It takes five men and a crane
to heave the 300 kilogram hydrant into place.
They're trying to connect the hydrant
to an older section of branch pipe.
And however many ways they try, it doesn't fit.
Being that you're trying to repair something
that was installed between, say, 1900 and 1960s,
it makes the job very challenging.
May not know if the job's going to take one hour
or two hours.
(indistinct)
Right now there is no space.
We're gonna have to cut the existing hydrant branch back
a little more towards the street
to give us a little more room.
The hydrant needs to fit perfectly.
A centimeter out
and it will leak valuable water and pressure
needed in the event of a fire.
The team need to shave off some of the existing iron pipe
to get it to the right size.
At times it can be frustrating,
especially if you're working in any kind of weather.
But today, right now, it's a nice day.
So it's just part of the game.
You want everything to run smoothly
but you expect little problems to go little by little.
Try to get past all the bumps in the road.
Not knowing what they're going to find
every time they dig up the road
is part of the job for John and his team.
Each job is much different
which makes it very interesting,
each day to day job.
At the end of the day, the jobs all get completed.
All the guys come in,
come into work safe and then go home safe.
The branch pipe sits right next to a network
of vital city services.
The team must be careful not to puncture gas, water,
telephone and internet lines.
There's a lot of utilities in the way.
Steam means and electric lines,
oil and static lines.
So it's much harder to repair the hydrants.
Finally the pipe is down to size
and the workers try the installation again,
this time it works.
But the job isn't quite over.
The team must check all valves are tightened securely
to avoid any valuable water seeping out
and that the hydrant drains its own water correctly.
The last step in installing a hydrant
is making sure that the gasket and the retaining gland
and the bolts are tight
and you have the backing in the back of the hydrant
so when you open it up,
any pressure against the hydrant, it's fine.
And you open it up to make sure it's running fine as well.
Once the final checks are made,
the surface area is restored with a layer of concrete.
But they take for granted
the work that goes behind the hydrant to keep it working.
This hydrant is now ready for action,
along with the other 110,000 in the city.
It's been a challenging day for the team
as they continue to keep New York
armed against the flames.
Moving water in and out of our cities
is vital to our survival.
Protecting and maintaining the structures
that make this possible is a massive challenge.
In San Francisco, the threat to its water infrastructure
is much greater.
In the next 20 years,
the chance of an earthquake of 6.0 magnitude or higher
hitting the area is as high as 60%.
To avoid complete collapse,
the city is defending one of its oldest structures,
its sewer system, against the next big one.
Today, veterans sewer inspectors, Lorenzo Hale
and Fred Gonzalez are assessing a section of the sewer
for structural damage.
But before their descent, they must check
for a dangerous occupational hazard, methane gas.
We're about to put the gas meter
hose inside the pit hole here just to test the atmosphere
for any toxic gas or any methane,
cause any little spark, if it's methane gas,
could cause an explosion.
The guys have the go-ahead
but for their own safety,
they have just one hour underground
before they must resurface.
San Francisco has one of the oldest sewers in the US.
Originally built for a population
of approximately 50,000 people,
it's now a wastewater network for a city 16 times that size.
It spans a staggering 1500 kilometers
and can carry over one billion liters
of city wastewater a day.
The stress this puts on older sections of the network
weakens its structure considerably.
And it's Fred Gonzalez's job to protect it from collapse.
99% Of the people
probably don't even realize what's underneath the city.
Until they have a problem,
nobody really cares or understands
what goes on under the ground.
Their workspace is cramped, hot and dark.
What we look for in this joint
is any sand coming through
or any kind of infiltration of water.
Sand coming through a joint in the tunnel
indicates a weakness that in the event of an earthquake
could cause a total collapse.
What happens is if sand starts coming through,
there's no sand between this and the street.
If enough sand washes away and a bus drives over it,
the bus will actually fall into a hole.
This joint is looking good for now,
but a section of the wall further along the tunnel
is cause for concern.
The wall has been damaged during the winter rainy season
when these tunnels run at full capacity.
If you look right here, all these here is signs.
At one time, the water level was this high,
up to here.
All these are all remnants of toilet paper
and stuff that sticks to the wall.
So when it rains, this runs full capacity almost.
This sewer collects more than 300 million
liters of wastewater a day,
enough water to fill 120 Olympic size swimming pools.
But when it rains heavily,
it can be six times that amount of water.
After every rainy season,
we've got to really inspect these big sewers
because that's when a lot of damage is being done
which is gonna just cause big problems later.
(tension music)
Structural weaknesses in any part of the sewer
must be dealt with straight away.
Just marking the wall of this mine to be plastered.
Lorenzo and Fred have reached their time limit
and climb up to fresher air,
but the job isn't quite finished.
A team of plasterers is on its way
to carry out the emergency repair.
Strengthening this small section of sewer
looks simple enough.
But like Lorenzo and Fred,
this team has a short window of time
in which to carry out their work.
Potentially, toxic gases and dark and damp conditions
mean workers can't stay underground for more than an hour.
This constant cycle of inspection and repair
is the only way to keep San Francisco sewage structure safe.
These aren't the sewer's only hidden heroes.
Across the city, another rapid response team
has received a call out.
(upbeat music)
People might wash a lotta grease down the drain
and over a period of time it blocks the drain.
Or they might
flush too much toilet paper.
There's a blockage
in one of the smaller sewer pipes
that connects the main drain,
causing raw sewage to leak onto the streets.
Veteran service engineer, Jose Ledesma,
is proud of his part in keeping sewage flowing
under the city.
I've been working for this sewer word department
for 16 years
and I've been doing this kind of work for 30, 35 years now.
And I'm impressed with what San Francisco has got.
It's got good equipment,
good tools for the sewer problems that we encounter.
And today is no different.
We're responding to an emergency.
It's actually called a side service emergency backup.
What it's doing, it's overflowing.
It's not going out to the main.
But the size of the pipe
means that Jose can't go down to fix it.
Instead, it's a job for Betsy.
This is it.
This is the one that gets all the work done, right here.
Betsy is a 60 centimeter long
stainless steel explosion-proof video camera
that can get to places humans can't.
On this job, Jose and Warren Best
are hoping she can show them what the mystery blockage is.
It's a tool.
You gotta treat it like part,
part of your job.
Without this here, you can't do nothing.
We ain't gonna have no results on what the problem is.
Betsy's always gonna get the job done.
From the back of the van,
Warren controls Betsy as she travels down into the depths
of the sewer.
We need to pan and tilt, basically,
to see 360 degrees of the pipe.
Any defects that we might have, you know, in the pipe.
All right, right here I'mma increase the speed.
15 meters into her search
and Betsy comes across the problem area.
A large amount of grease from a nearby restaurant
has built up in the pipe.
It needs to be removed and it's Don's job to dislodge it
with a high pressure hose and an industrial solvent capable
of breaking down the grease.
But the cause of the blockage is the usual offending items.
Paper towels are bad.
Diapers too. They don't break down.
Paper towels and diapers
get absorbed, like they could splash,
blow up like 10 times of the volume.
The jets works the blockage free.
It's another battle won for the emergency team.
But maintenance alone is not enough
to keep a city's sewage system working.
In downtown San Francisco,
critical construction work is being carried out
to protect a main wastewater pipe from collapse.
The north shore force main,
a pressurized pipe over two kilometers long
moves untreated wastewater through the city
but it has failed twice in the last five years.
A bypass pipe is being built
while vital repairs are carried out on the main pipe.
This requires digging up the road
right in the heart of the city.
Construction in a city like San Francisco
is very challenging.
We're really webbing through a jungle of infrastructure
when we're trying to replace a soar line.
The team make every effort
to reduce the amount of road surface they need to dig up,
but there's no escaping the dangers
of working in this densely populated area.
Where we are right now,
it's the heart of the financial district.
We have apartments, condominiums, tourists,
visitors, workers, commuters.
During any given day,
the population of San Francisco doubles
when the workforce enters the city.
So we have to maintain that support.
Despite these challenges,
round the clock maintenance and new construction
play a vital part in keeping the city's wastewater
flowing out safely.
But it's only half the battle.
If left untreated, wastewater can spread disease.
The average city dweller uses approximately 200 liters
of water a day,
flushing the toilet,
taking a shower or doing the washing up.
In Stockholm, over 350 million liters go down the plug hole
on a daily basis.
And it ends up here.
This is Henriksdal,
one of the largest underground wastewater treatment plants
in the world.
It's so vast, operating technician Dennis Goffin
depends on his scooter to get around the plant.
Its about 20 kilometers of tunnels,
300,000 square meters of area.
Seven digesters,
about 30 tanks.
It's a big place.
One second you're sitting here in front of a computer screen
and the other second you're down in like
one of the filthiest places in Stockholm.
Dennis is one of a team of 28
whose job it is to process millions of liters
of wastewater a day
disposed of by over 700,000 people.
But after so long in the job,
Dennis no longer thinks about where the waste has come from.
I don't even think that it's people's waste anymore.
I just think that it's just some dirty mess
that has to be cleaned.
You don't even consider that it comes from someone.
Most impressively, 98% of the waste water
that comes through Henriksdal
goes back into the Baltic Sea, clean enough to swim in.
Stockholm is islands and water.
That's all it is.
So we have to protect that environment.
That's why it's important to keep this process going
and keep it getting better each day.
It's a mammoth task.
In the plants control room,
computers monitor the intake
of thousands of liters per second,
which varies based on the time of day.
So here we can see that it fluctuates
in the middle of the day.
It gets us
about 3000 and then at nighttime all the way down
to only 1000, even below that sometimes.
Waste rush hour is right now at 7:00 a.m.
As Stockholm's residents all head to the bathroom,
the plant can often run over full capacity.
We can see that about 12,000 liters a second came in
and that causes trouble.
In just one hour,
the plant is capable of ingesting over
36 million liters of wastewater.
And down in the depths of the mountain,
Dennis' colleague process engineer Hannah Astfelt,
is heading off to monitor the first stage
of the cleaning process.
Henriksdal has a surface area
the size of over 30 football pitches.
Like Dennis, the only way for Hannah to get around
to complete her morning checks
is to take the latest model of sewage plant transport.
Everybody needs a bike or a moped to work here.
This motorized trait is a definite upside
to a job that sees Hannah exposed to thousands of liters
of her fellow residents' waste.
As we can see, there's a lot of debris from the humans.
There's
sanitary articles, condoms,
food.
Step screens extract any debris
bigger than three millimeters from the water.
That includes 10 tons of earbuds,
tampons and condoms a week.
These items could cause devastating damage
to machinery and bring the plant to a halt.
I think people sort of think
that they can throw anything into toilet,
but for us it's a big problem
because these material
creates a great damage
if they continue for the process.
But the items aren't limited
to what goes down the toilet.
The city's drains also empty into this facility
with some surprising results.
A bicycle, a canoe,
and we have seen driving license
and even teeth from people.
So I don't think we can be any more shocked.
Here at the sediment tanks,
gravity does the work.
Solid matter or sludge sinks to the bottom
whilst cleaner water flows from the top.
But it doesn't always go to plan.
Today, Dennis and Hannah have noticed something strange
during their daily inspection,
an abnormal buildup of sludge.
We're seeing sludge that should be sinking,
but for one reason or another
some bad bacteria is formed
and not been taken care of
in the biological cleaning process
which means it comes down to this process
and creates these carpets which causes it to float up.
With epic volumes of wastewater
to process every day, Hannah and Dennis can't afford
to let one defect in the chain affect the next.
However small a problem, it could escalate
in a matter of minutes
and have a detrimental effect on the quality of clean water
going out of the plant.
The team leave nothing to chance
and draft in another young member
who gives the sludge a helping hand to sink to the bottom.
This is the regular everyday business,
to just go through the entire process.
Does it smell bad?
That means it's probably a problem somewhere.
Does it look bad?
My girlfriend doesn't know what my job entails.
No one knows what I work with.
People don't even know how big this place is.
One of the final processes
known as the biological stage
is critical to making this water clean enough to swim in.
And it's completely invisible.
Good bacteria devours the organic matter
and nitrogen in the waste.
And 24 hours later, the result is this,
water in this jacuzzi style outflow
is on its way back to the Baltic Sea
at an average speed of 2000 liters per second.
Our job is to clean the water
from this dirty mess that we saw
into water that we can actually put back into the Baltic Sea
with a clear conscience.
You don't have to go back that far
to see a time where you could not swim in Stockholm.
It was actually illegal to swim
anywhere in the city of Stockholm
and now you can swim anywhere.
You can ask anyone in Stockholm.
In most water treatment plants,
this is where the story ends,
but Henriksdal is one of the few plants around the world
reducing the amount of water waste even further.
While some plants discard their sludge,
Dennis and his team consider it
one of their most prized products.
Well here we mix the primary sludge
with the secondary sludge,
with the organic matter that comes into our organic station.
This all gets mixed together.
And with these pumps,
pumps into the digesters to begin creating biogas.
Our advantage is that we are so big,
that we get so much in,
that we can actually do this stuff,
that we can actually make this much gas.
After leaving Henriksdal,
waste matter goes through a further refining stage
before arriving at Keolis bus depot in the form of biogas.
Here, a fleet of about 120 buses
take minutes to fuel after a 22 hour shift
on the city's roads.
But the difference is that this biogas
is entirely renewable and much less polluting
than ethanol or diesel.
It's the way forward for technical advisor, Eric Norden.
I'm proud to say that our fleet here runs on biogas.
I would like more companies to go with it because it's good.
It's really good.
It's actually amazing that you can make fuel other ways.
You know, people flush their toilets
and it turns into fuel for cars and buses.
Henriksdal turns a record
one and three quarter trillion liters of wastewater a week
back into clean water and biofuel,
making this plant a model for the future.
(lighthearted music)
Cities around the world depend on the skill of engineers,
scientists, inspectors and technicians
to keep our water flowing.
Without this hidden army working tirelessly
around the clock,
our survival, well-being, safety and prosperity
would be seriously at risk.