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Water Filtration Is Being Revolutionized by What Scientists Found
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Posted by Okachinepa on 12/12/2024 @
Courtesy of SynEvol
Credit: Jennifer Chu
From microscopic crustaceans, corals, and krill to larger creatures like mollusks, barnacles, basking sharks, and baleen whales, filter feeders may be found all over the animal kingdom. The mobula ray, one of these filter feeders, has developed a special feeding technique that may lead to improved industrial water filter designs, according to MIT experts.
Researchers have described the filter-feeding system of the mobula ray, a group of aquatic rays that comprises seven devil ray species and two manta ray species, in a publication published in the Proceedings of the National Academy of Sciences. As water enters their mouths and exits through their gills, mobula rays catch plankton by swimming through plankton-rich waters with their mouths wide open.
Water is directed toward the ray's gills by means of parallel, comb-like structures called plates that run the length of its mouth. These carefully placed plates, according to the MIT team, force plankton particles to bounce deeper into the ray's mouth rather than escape via its gills. Furthermore, the gills draw oxygen from the water that is expelled, enabling the ray to simultaneously breathe and feed.
According to study author Anette "Peko" Hosoi, a Pappalardo Professor of Mechanical Engineering at MIT, "we demonstrate that the mobula ray has evolved the geometry of these plates to be the ideal size to balance feeding and breathing."
Courtesy of SynEvol
Credit: Jennifer Chu
Inspired by the mobula ray's plankton-filtering capabilities, the engineers created a basic water filter. They examined the water flow through the filter after it was equipped with features that resembled 3D-printed plates. The scientists used the findings of these trials to create a blueprint that they claim designers may utilize to maximize industrial cross-flow filters, which share many of the mobula ray's configurations.
Lead author and MIT postdoc Xinyu Mao PhD '24 states, "We want to expand the design space of traditional cross-flow filtration with new knowledge from the manta ray." "People may be able to enhance overall filter performance by selecting a parameter regime of the mobula ray."
Courtesy of SynEvol
Credit: Jennifer Chu
The group's concentration on filtration during the height of the Covid pandemic, when they were creating face masks to filter out the virus, gave rise to the latest study. Since then, Mao has turned his attention to researching animal filtration and how specific filter-feeding mechanisms could enhance industrial filters, including those found in water treatment facilities.
Permeability, or how easily a fluid can pass through a filter, and selectivity, or how well a filter blocks out particles of a particular size, must be balanced in any industrial filter, according to Mao. A membrane studded with big holes, for example, may be very permeable, allowing a lot of water to pass through with relatively little energy. However, the membrane would have very little selectivity because of its enormous holes, which would allow many particles to pass through. Similarly, a membrane with a lot fewer pores would be more discriminating, but it would also need more energy to force the water through the tiny holes.
"How can we improve upon this trade-off between permeability and selectivity?" we questioned ourselves. Hosoi says.
Mao discovered that the mobula ray had achieved the perfect balance between permeability and selectivity when researching filter-feeding animals: Because of its high permeability, the ray can swiftly draw water into its mouth and expel it through its gills, allowing it to breathe in oxygen. In addition, it is extremely selective, filtering and consuming plankton instead of allowing the particles to pass through its gills.
The ray's filtering characteristics, the researchers discovered, are largely comparable to those of industrial cross-flow filters. These filters are made so that fluid passes over a permeable membrane, which allows the majority of the fluid to pass through, while any pollutants continue to pass through the membrane and finally exit into a waste reservoir.
The group pondered whether the mobula ray could serve as an inspiration for better industrial cross-flow filter designs. They did it by delving further into the dynamics of mobula ray filtration.
The team created a straightforward filter based on the mobula ray as part of their latest investigation. The filter's architecture is essentially a pipe with holes along its sides, or what engineers call a "leaky channel." The team's "channel" in this instance is made up of two clear, flat acrylic plates that are adhered to one another at the edges and have a little gap between them that allows fluid to be pumped through. The researchers placed 3D-printed structures at one end of the tube that resembled the grooved plates that run along the mobula ray's mouth floor.
In order to visualize the flow, the team then pumped water through the pipe at different rates while adding colored dye. Photographing the channel, they saw an intriguing change: the flow was "very peaceful" at low pumping rates, and fluid flowed readily between the printed plates' grooves and out into a reservoir. The faster-flowing fluid did not slide through when the researchers increased the pumping rate; instead, it seemed to swirl at the opening of each groove, forming a vortex that resembled a little knot of hair between the tips of a comb's teeth.
According to Hosoi, "this vortex is blocking particles, not water." At faster flow rates, particles attempt to pass through the filter but are thwarted by this vortex and are instead blasted down the channel, whereas at a slower flow, particles pass through the filter with the water. Because it stops particles from flowing out, the vortex is useful.
The researchers created a cross-flow filtration plan using the dimensions of the mobula rays' filtering properties and the outcomes of their trials.
Mao says, "We have given useful advice on how to really filter as the mobula ray does."
According to Hosoi, "you want to design a filter and be in the regime where you generate vortices." According to our instructions, your filter must have a specific pore diameter and spacing in order to create vortices that will filter out particles of this size if you want your plant to pump at a specific rate. We have a really useful guideline for rational design from the mobula ray.
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