Submission + - Fish-inspired filter removes 99% of microplastics from washing machine wastewate (techxplore.com)
schwit1 writes: Some fish feed by means of filtration; these include, for example, mackerel, sardines, and anchovies. They swim through the water with their mouths open and sift out the plankton with their gill arch system. "We took a closer look at the construction of this system and used it as the model for developing a filter that can be used in washing machines," says Blanke, who is a member of the transdisciplinary research areas Life & Health and Sustainable Futures at the University of Bonn.
During their evolution, these fish have developed a technique similar to cross-flow filtration. Their gill arch system is shaped like a funnel that is widest at the fish's mouth and tapers towards their gullet. The walls of the funnel are shaped by the branchial arches. These feature comb-like structures, the arches, which are themselves covered in small teeth. This creates a kind of mesh that is stretched by the branchial arches.
The filter element in the center imitates the gill arch system of the fish. The filter housing enables periodic cleaning and installation in washing machines.
"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," explains 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."
This principle prevents the filter from being blocked—instead of hitting the filter head-on, the fibers roll along it toward the gullet. The process is also highly effective, as it removes almost all of the plankton from the water. Both are aspects that a microplastic filter must also be able to deliver. The researchers thus replicated the gill arch system. In doing so, they varied both the mesh size of the sieve structure and the opening angle of the funnel.
"We have thus found a combination of parameters that enable our filter to separate more than 99% of the microplastics out of the water but not become blocked," says Hamann. To achieve this, the team used not only experiments but also computer simulations. The filter modeled on nature does not contain any elaborate mechanics and should thus be very inexpensive to manufacture.
The microplastics that it filters out of the washing water collect in the filter outlet and are then suctioned away several times a minute. According to the researcher, who has now moved to the University of Alberta in Edmonton, Canada, they could then, for example, be pressed in the machine to remove the remaining water. The plastic pellet created in this manner could then be removed every few dozen washes and disposed of with general waste.
During their evolution, these fish have developed a technique similar to cross-flow filtration. Their gill arch system is shaped like a funnel that is widest at the fish's mouth and tapers towards their gullet. The walls of the funnel are shaped by the branchial arches. These feature comb-like structures, the arches, which are themselves covered in small teeth. This creates a kind of mesh that is stretched by the branchial arches.
The filter element in the center imitates the gill arch system of the fish. The filter housing enables periodic cleaning and installation in washing machines.
"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," explains 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."
This principle prevents the filter from being blocked—instead of hitting the filter head-on, the fibers roll along it toward the gullet. The process is also highly effective, as it removes almost all of the plankton from the water. Both are aspects that a microplastic filter must also be able to deliver. The researchers thus replicated the gill arch system. In doing so, they varied both the mesh size of the sieve structure and the opening angle of the funnel.
"We have thus found a combination of parameters that enable our filter to separate more than 99% of the microplastics out of the water but not become blocked," says Hamann. To achieve this, the team used not only experiments but also computer simulations. The filter modeled on nature does not contain any elaborate mechanics and should thus be very inexpensive to manufacture.
The microplastics that it filters out of the washing water collect in the filter outlet and are then suctioned away several times a minute. According to the researcher, who has now moved to the University of Alberta in Edmonton, Canada, they could then, for example, be pressed in the machine to remove the remaining water. The plastic pellet created in this manner could then be removed every few dozen washes and disposed of with general waste.
