Fish gills may inspire an unexpected solution to one of our biggest sources of microplastics. According to researchers at Germany’s University of Bonn, taking a cue from the animals’ filtration systems might help remove the vast majority of harmful plastic particulates from washing machine wastewater.
Microplastics are a huge problem. At this point, they can be found both inside our bodies as well as some of the Earth’s most remote locations. Aside from taking thousands of years to decompose, the particles are increasingly linked to a wide array of health issues.
Our dirty laundry sneakily contributes to a huge amount of microplastics. Researchers estimate a washing machine in a four-person home produces as much as 500 grams of microplastics every year due to textile abrasion and deterioration. These removed clothing particles then travel with the wastewater into sewer systems and eventually treatment facilities. Because portions of sewage are often integrated into agricultural fertilizer, the microplastics ultimately find their way onto farmlands.
University of Bonn biologist and study co-author Leandra Hamann explained that while washing machines often include various filter systems, they’re far from perfect.
“Some of them quickly become clogged, others do not offer adequate filtration,” Hamann said in a statement.
According to Hamann, designing alternative filtration methods could dramatically reduce laundry’s mountains of microplastic material. Instead of investigating advanced engineering concepts, she and her team looked to millions of years of animal evolution for inspiration.
Fish like sardines, anchovies, and mackerel feature funnel-shaped gill arch systems that work similarly to a cross-flow filtration system. As water travels through their mouths and down their gullets, comb-like formations covered with tiny teeth form a stretchy mesh that screens out unwanted particles. A gill arch system works as both a filter and a means to catch a fish’s next meal.
“During food intake, the water flows through the permeable funnel wall, is filtered, and the particle-free water is then released back into the environment via the gills,” added biologist and study co-author Alexander Blanke. “However, the plankton is too big for this; it is held back by the natural sieve structure. Thanks to the funnel shape, it then rolls toward the gullet, where it is collected until the fish swallows, which empties and cleans the system.”
It’s a crafty bit of evolution. Because the arches roll toward the gullet, it’s much harder for particles to clog the filter.
After experimenting with various mesh sizes and funnel opening angles, Hamann and her colleagues settled on a design that rivals all those eons of evolutionary fine-tuning.
“We have thus found a combination of parameters that enable our filter to separate more than 99 percent of the microplastics out of the water but not become blocked,” Hamann said.
Once the microplastics are captured, the system collects them in a filter outlet before suctioning them out multiple times per minute. The team suggests that with minor alterations to a washing machine, the appliance could ultimately press the plastic to remove excess water before molding it into a pellet. After a few dozen washes, an owner could simply remove the plastic block and dispose of it properly in their general waste.
The study’s authors also say that their new filter doesn’t require complex mechanical parts and is extremely cheap to produce. With a patent now pending, the team hopes washing machine manufacturers will soon help improve the system and integrate them into their own products.
