How To Clean Up The World’s Most Polluted Rivers
It’s estimated that every year, millions of tons of plastic enter the ocean through rivers, and as global waste generation increases, the problem is poised to worsen. But a host of companies from Baltimore, Maryland to Bengaluru, India are working on the issue, developing novel methods to capture trash from rivers before it reaches the ocean.
In Baltimore, Maryland, these river cleanup devices
have become local celebrities.
And we have Mister Trash Wheel, Captain Trash Wheel,
Professor Trash Wheel and Gwynnda the Good Wheel of
the West here in Baltimore.
These four wheels are powered by the sun and the
waves, and they’re one of an increasing number of
systems working to remove trash from waterways.
Because while the public has become highly aware of
the massive gyres of waste swirling in our oceans, we
tend to hear less about how it all ended up there.
I wouldn’t be surprised if the amount of plastics in
all the rivers around the world is much more than all
the plastics that is in the oceans.
Every year, it’s estimated that up to 2.97 million tons
of plastic enters the ocean through rivers, much of it
originating from areas of the world that lack proper
waste management infrastructure.
And then when it rains, it washes all of this trash
through these water stream, that ultimately ends up in
the river, that ends up in the ocean.
And waste generation overall is only expected to increase
in the years to come.
So in 2020, the waste that we generated was about 2.2
billion tons. And we’re estimating that by 2050,
we’ll be generating about 3.9 billion tons.
The ultimate solution to the waste problem depends on
some combination of better waste infrastructure, more
sustainable packaging, less consumption, and public
awareness around proper disposal. But in the
meantime, there’s a host of companies around the world
developing systems to capture wayward trash from
We’ve been averaging about 30 tons a month, picking up
trash from the waterways of Baltimore.
We currently have four types of interceptor deployed in
We have cleaned a couple of rivers and maybe 10,000 tons
of plastic stopped from reaching the ocean.
Heavy rains and winds often carry trash from the land to
the rivers, a particular problem in low-income
countries such as those in Sub-Saharan Africa, where
the majority of the waste generated is never even
collected, especially in rural areas.
And even when that waste is collected, it doesn’t mean
it’s being properly disposed of.
In those countries, nearly 40% of waste is being
collected, but then more than 90% is just being
openly dumped or burned.
So there’s still that disconnect that even when
waste is collected, it can still be dumped in more
informal dump sites.
Waste from these informal dump sites often migrates
into rivers, and middle-income countries like
the Philippines, India, and Malaysia actually contribute
the most to oceanic waste, as people have enough money
to buy lots of packaged goods, but waste collection
infrastructure still lags behind.
So that’s why this middle ground is where you see most
plastic leakage to the oceans, which tend to be
areas in Southeast Asia, Central Africa, and Central
Of all the plastic that enters the ocean through
rivers, nearly 80% is transported through 1,000
That’s according to a 2021 study funded by the Ocean
Cleanup, the Dutch nonprofit founded in 2013 by
then, 18-year-old Boyan Slat.
That’s a lot more rivers than The Ocean Cleanup and
other researchers had previously thought, as a
2017 study had indicated that a mere ten rivers were
the primary culprits.
The types of rivers that we now think contribute most to
river plastic export into the ocean are smaller rivers
flowing through urbanized areas rather than the
typical very large river systems.
Van Emmerik helped co-author the 2021 study and says that
the other primary finding is that the grand majority
of plastic pollution never actually makes it into the
ocean at all. So if the goal is to reduce the total
amount of plastic in our environment, that makes it
even more important to tackle plastic pollution
closer to the source, as opposed to pulling it from
the ocean after the fact.
That’s something that Clearwater Mills, The Ocean
Cleanup and the India-based company AlphaMERS are all
trying to do.
Baltimore’s googly-eyed trash wheels, the first of
which debuted in 2014, are one of the original efforts
to address river waste.
Built by Clearwater Mills, the company’s founder, John
Kellett, was inspired to design the wheels after
years of seeing trash pouring into the Baltimore
Harbor after big storms.
It comes from land sources, it comes from the streets,
the parking lots, the alleys, the highways.
And when it rains, it gets washed down the storm drains
and into the small creeks and then into the rivers
that feed the harbor.
Containment booms are set up in a V-shape across the
river, with rubber skirts that extend about two feet
below the water’s surface with weights on the bottom.
This catches trash floating downriver and funnels it
towards the mouth of the rotating trash wheel, which
is powered by the river’s current and attached solar
panels. As the wheel turns, it powers a conveyor belt
that lifts trash out and deposits it into a dumpster.
And the dumpster is on a separate floating barge, and
when that dumpster is full, we have another floating
barge that we bring with an empty dumpster.
Take the full one out, slide the empty one in and
keep picking up the trash.
The four wheels have picked up a total of about 2,000
tons of trash and debris, including organic material
like sticks and leaves, which actually make up the
bulk of the weight, since plastic is so light.
But that haul overall includes about 1.5 million
plastic bottles, 1.4 million foam containers and
12.6 million cigaret butts.
Everything is then incinerated in a
Installing a new wheel costs anywhere from $400,000
to $1.5 million and up, depending on local river
conditions, waste infrastructure, and
Operating costs also vary widely, from $18,000 to over
$100,000 per year.
Though it can get pricey, Kellett says that solutions
like this are cost-effective compared to
the massive externalities incurred from plastic
pollution in our waters, like the impact on marine
life and microplastic contamination of food and
What we’re doing with plastics and the way we’re
dealing with them now has costs associated with it.
You can’t really keep doing what we’ve been doing.
So how are you going to fund a new way of doing
Three of the wheels are owned and funded by the
Waterfront Partnership of Baltimore, an NGO, and one
is owned by the state government. Additional trash
wheels are planned for Texas, California, and even
Panama, where a local nonprofit, Marea Verde, has
partnered with Clearwater Mills to build the fifth
wheel in the family, named Wanda Díaz.
This project is funded by the Benioff Ocean Initiative
and the Coca-Cola Foundation, which together
are supporting a portfolio of river cleanup projects
around the world.
So we started the construction of the device,
of Wanda, a couple of months ago.
Clearwater Meals, their team and even the creator,
John Kellett, they came down here to Panama to help
us with the installation.
Wanda will operate on the Juan Díaz River.
As one of the most polluted rivers in Panama, it sees a
much heavier trash flow than Baltimore’s rivers,
especially after the first rains of the season.
But Watemberg is confident in the technology.
So we are very hopeful that this will be a very big
success for our country.
But at the end of the day, this is not something
sustainable. We cannot have thousands of projects like
this running forever.
You know, the real solution to this problem is
behavioral change, education, changing the way
we’re consuming goods.
The Ocean Cleanup is probably best known for its
efforts to clean the Great Pacific Garbage Patch, an
endeavor the company’s young founder, Boyan Slat,
started pursuing in 2013 after a TED talk he gave on
the topic went viral. Now though, the company is
pursuing a dual focus, as it’s built a series of river
Our goal is to rid the oceans of plastic.
And the reason why we look at rivers is because we
believe it’s the fastest and most cost-effective way
to prevent further plastic from being emitted to the
The Ocean Cleanup’s first river cleanup device, called
the Interceptor Original, was released in 2019.
It’s a fully solar-powered barge that operates much
like Baltimore’s trash wheels, just on a larger
scale. Sitting at the mouth of a river, it funnels trash
onto a conveyor belt and automatically distributes
the waste across six giant dumpsters, which can hold
over 17,000 cubic feet of trash.
Where the trash goes after that depends on the country
and the infrastructure that it has.
Some is sorted and recycled, some is burned in
waste-to-energy facilities, and some is landfilled.
But since this giant interceptor doesn’t fit in
smaller rivers, the team developed another solution
That’s why we also introduced now something
called the Interceptor Barrier, essentially a
barrier you put at the mouth of the river.
We have an Interceptor Tender, which is a mobile
conveyor belt, which then can scoop out the trash from
these barriers, which we now applied in Jamaica,
where the rivers are simply too narrow and too shallow
to fit an original interceptor.
And for the most severely trash-choked rivers, The
Ocean Cleanup is developing another solution called the
Trashfence, which it’s piloting in Guatemala.
The concept is simple. A 26-foot high steel fence,
anchored to the bed of the river, stops the flow of
trash during a big storm.
Then, after the water level recedes, excavators remove
the waste. But the onslaught of trash in one of
the world’s most polluted rivers proved too intense
for version 1.0.
The force of the trash was so high that the Trashfence
failed, unfortunately. So we’re now working on the
version two that will hopefully be ready for the
next rainy season.
Like Baltimore’s trash wheels, costs are very
location dependent. But Slat says that getting an
interceptor up and running is generally a
multimillion-dollar project, paid for by
philanthropic donations, corporate partnerships, and
local governments. Eight Ocean Cleanup interceptors
are currently installed in Indonesia, Malaysia,
Vietnam, the Dominican Republic, and Jamaica.
The Trashfence in Guatemala is undergoing maintenance,
and more cleanup devices are in the pipeline,
including one in Los Angeles.
We’ll be about 20 towards the end of the year,
beginning of next year. And ultimately, we hope to scale
this exponential trend.
India-based company AlphaMERS makes another
version of a river barrier.
With 34 installations in eight different cities, this
barrier is relatively low-tech and low-cost.
It’s much smaller than the Ocean Cleanup’s Trashfence,
and not designed for the same extreme trash flow.
But it’s still pretty heavy duty. Made of stainless
steel mesh, the AlphaMERS fence floats a couple feet
above and below the water level.
The hydrodynamics and the hydrostatics of this is very
simple but excellent for the job.
And it’s made very rugged, very heavy duty, with steel
chains holding it on both sides.
So it’s able to withstand the monsoon flows
immediately after the rain.
Sekhar says his floating fence excels at stopping
trash and rivers with fast currents, whereas designs
that rely on a boom and a skirt might fail when
currents pick up, since the water will instead run over
the barrier, bringing trash with it.
Eight floating barriers were deployed at various
points along the Cooum River in Chennai in 2017, at
a cost of about $125,000.
And in their first year of operation, Sekhar says they
captured about 2,400 tons of plastic.
The barriers are angled to direct trash towards the
riverbank, where traditionally excavators
have been used to pluck the trash from rivers, a cost
not factored into the installation expense.
But lately, AlphaMERS has been using conveyor belts as
Clearwater Mills in The Ocean Cleanup do.
Now we have started with the conveyor belts.
One end is floating, one and is on the land.
And now it’s run with electrical power, with
portable generators, but very soon we will run it
with the flow of river water.
Sekhar says the barriers are financed by municipal
governments and corporations with social
While in the future, he hopes to use AI to identify
the types of waste being collected and where it
originates from, for now, AlphaMERS is focused on its
straightforward cleanup strategy.
We like to take the simplest solution and work upwards.
And artificial intelligence and machine learning is the
last priority in our scheme of things.
As these various wheels, barriers, and fences are
deployed in more locales around the world, it will
become clearer and clearer what technologies are best
suited to what environments. And given the
magnitude of the waste problem, there’s more than
enough room for all the players in this space.
The goal is not to have 1,000 interceptors in the
world, but to solve the top 1,000 heaviest polluting
rivers. And any river that anyone else solves is one
river less for us to to worry about.
So the more the merrier.
But all these organizations are well aware that these
river cleanup systems are not the ultimate solution to
our waste problem.
One of the things we’re looking forward to is when
trash wheels are no longer needed, when we’re
addressing the problem upstream to the extent where
no trash is entering our waterway and we don’t need
to have a trash wheel.
Of course, financing waste cleanup, collection, and
management around the world is a challenge.
And Kaza says that the World Bank is always
thinking about ways to incentivize citizens and
governments alike to pay for long-term waste
There are models where there’s cross subsidization.
Wealthier communities pay a bit more than than
We’ve seen models where people pay based on the
volume of waste they generate.
And we’ve seen waste fees increase over time as
services are proven, that was very effective.
Funding models aside, though, Watemberg emphasizes
that the desire for change has to first come from the
If we don’t change our habits and if we don’t work
with communities and if we don’t look for alternatives
and different solutions on land, this is not going to
end. So we need people to come together as a
community, as a country, with authorities, without
authorities. We need everything.
At the end of the day, funds are important, but we
need to start with our will to do it.