LifeStraw is a portable, personal water filter that uses hollow fiber membranes with microscopic pores that can block bacteria, parasites, and microplastics. With use, the membrane gradually accumulates contaminants starting at the inlet.

We scanned a new reverse osmosis filter, ran it for two months in a hard-water environment, and scanned it again. Scaling deposits of minerals are clearly visible in the used-filter CT scan. As they accumulate, they restrict flow through the filter and reduce efficiency.

Reverse osmosis water filters use a semi-permiable membrane made of tightly-wound layers of synthetic material. They’re used in both small residential applications as well as giant industrial water treatment operations.

The water’s flow pattern is clearly visible in the medium: water flows in along the outer edges of the cartridge, then through the medium to the center channel before heading to the refrigerator’s ice maker.

Here’s a CT scan of an activated charcoal water filter from a Bosch refrigerator. The manufacturer recommends changing it every 6 months, but this was in my fridge for more than two years 😱

Here we’ve used @lumafield’s automated inclusion analysis tool to identify areas that are particularly dense. The densest impurities, highlighted as purple and red specks, have been getting strained out toward the top of the filter medium.

As the filter medium inside this Brita cartridge is used, it swells and cracks. Clearly-defined flow channels are visible, suggesting water is following the same path through the filter media each time.

Industrial CT scans capture both geometry and density. We take X-ray images from different angles and reconstruct them into a 3D model. A dark area in a 2D X-ray could be either thicker or denser material; with CT we can separate geometry from density, shown in red/blue in this @lumafield scan.

These are before-and-after @lumafield scans of a @Brita water filter; it’s filled with a blend of activated carbon and ion-exchange resin and claims to trap chlorine, sediment, and heavy metals like lead. The filter medium swells with use, and it also gets denser. How do we know?

Do water filters actually do anything? We CT scanned several popular water filters before and after use to see what they’re able to keep out of your body. Here’s what we found… 🧵