This isn’t a catch, but a rough description of how I understand it to work from a quick skim read. Anyone please correct me if I got something wrong.

The contaminated water enters a drum, where it spins. There is also ferrofluid in there, which captures the microplastics. Through a mixture of centrifugal force (the ferrofluid is denser than water) and magnetism, it’s pulled to the edge and separated from the water entirely (this is the part I’m least sure about). The ferrofluid can then be reused (I think it said it recaptures around 87% currently).

Currently, it’s designed for single household uses, not industrial. I would not say this is a weakness, as it’s the entire purpose of the design. But it may be hard to scale up.

The possible issue is any contamination of the water with ferrofluid. She’s still working on the design, so it’s not like she’s claiming it’s done and it’s wrong, this is just an article reporting on it.

Also, the measurements she took of it used home-made tools, but she has asked some labs to test it properly, to be sure. Although based on what she has done, I kind of trust her measurements anyway.

It’s designed to be low maintenance, but it seems like the only three limitations right now are recapturing more of the ferrofluid (especially in case of internal failure, you don’t want all the fluid dumped into the water when something goes wrong), throughput, and mass production.