WC137 JulyAug 2024 - Magazine - Page 20
WASTEWATER
Nanoplastics were initially reported in the early 2000s. Since
then, they have been studied and are now known to cause adverse
effects on living organisms. They are defined as artificial polymer
particles with a size between 1nm and 1µm.
Nanoplastics are produced through the disintegration of plastic
products that are released into the environment. Microplastics, less
or equal to 5mm, degrade into nanoplastics. Nanoplastics originate
from two major sources—primary plastic waste and secondary
waste.
Tire wear and laundry wastewater are the two known largest
producers of nanoplastics in the environment.
Due to plastics being prevalent in every aspect of human society,
including containers, saleable water pipes, clothing, toys, medical
supplies, and automotive parts, studies indicate that virtually all
water bodies, air, soil, and food contain microplastic or nanoplastic
particles.
Because of their prevalence, humans are subjected to
nanoplastics throughout their lives. They can be absorbed into
the body through air inhalation, through the skin, and oral intake.
Nanoplastics can also be passed onto offspring.
Nanoplastics continue to be studied by scientists to determine
their effects on human health. It is known that they can cross the
blood-brain barrier as well as the placental barrier. They cannot,
however, pass directly through cell membranes, but they can destroy
cell membrane structure leading to cell death.
Source: National Library of Medicine
“If you expose it to high temperatures, nanoplastics can be
part of the activated carbon and we will be able to reuse the
activated carbon on several cycles,” he said. “That would be even
more appealing.”
Putting innovation to the test
The next step for experimentation is bringing this epoxy resin-based activated carbon to the scale of wastewater treatment
plants.
“The first few steps remove most of the debris and plastics,
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WATER C AN ADA • JULY/AUGUS T 2024
Creating a circular economy
What Mekonnen emphasizes is most important from this work
is not the chemistry used to carbonize epoxy resin, nor the
ability to remove nanoplastics from our waters. It’s the concept
of working towards a circular economy and taking a different
approach to how we think of plastics as a whole.
“If we leave plastics in their traditional form, as a one-way
avenue in a non-circular economy, that will be problematic,” he
said. “But, if we approach them through the circular lifecycle
platform, plastics can solve many problems. If we avoid them
completely, if we stop producing plastics completely, we will
have more problems than solutions.”
This is because a significant portion of our plastics are being
used to promote sustainability elsewhere. For example, in solar
panels or new cars that are now lighter and require less fuel to
power. It’s essential to consider what a world would look like
without plastics and the alternative chemicals or energy we
would rely on instead if plastics weren’t around.
“If you design your plastic in such a way that you know
about the end of its life, whether you’re recycling it or using it,
converting it to something else, you can have a more sustainable
system,” said Mekonnen.
It’s this thinking that has made this new method of capturing
nanoplastics in water a two-sided win: by giving life to plastic
waste and removing plastic waste all at the same time.
WAT E R C A N A D A . N E T
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NANOPLASTICS AND HUMAN HEALTH
including the microplastics, which are fairly easy to remove,”
added Mekonnen. “The nanoplastics are the most difficult, and
the current technology that’s implemented in our municipal
wastewater treatment system is not capturing them. The nanoplastics pass through, and it goes to our water bodies.”
Existing methods for removing nanoplastics in wastewater
treatment include ultracentrifugation and ultrafiltration. Both
rely on forcing water at high pressures through very fine membranes to capture nanoplastics. While effective, the intensive
energy requirements make these methods very costly.
Comparatively, when tested in labs, Mekonnen’s activated
carbon is effective without applying extreme force.
“It can move through gravity, or if you have to apply energy,
it will be very minimal energy. In our lab demonstration, we
didn’t use extra energy to pump water to capture nanoplastics at
94 per cent efficiency.”
Mekonnen and his team are now working with municipal
partners for testing. The team imagines using this activated carbon as the last step in water treatment via a packed column and
don’t anticipate the need for applying additional energy.
Another part of this challenge will be producing the amount
of activated carbon needed for these large treatment systems.
The team knows that theoretically they can further optimize
their yield, but more testing and funding are required.
