"Here is 1000 miles of railway. Each yard of that railway has 1000 lbs of crushed rock under it. Your job is to pick it all up, put it through this sieve, and put it back. I will employ you for $1 a month for 50 years to get the job done. Do we have a deal?"
No-one asked, but ... I worked at a power station one Summer, my job was to clean the filters at the bottom of the cooling tower. The filter was a stack of plastic bricks; each brick about 1m x 1m x 2m that were a mesh of orthogonal perforated plastic panels with a spacing of maybe 8cm or so. The filter was stacked about 5 "bricks" deep. We washed the bricks under a running hose of about 20cm diameter, standing in water all day; shaking out the mud. The bricks were heavy because they were full of what seemed like river mud. The detritus from the bricks fell down into the pond below the cooling tower, about 20m beneath us. Small skid-steer cat loaders dug out the pond.
I had a runner's build and was being paid £2.70 an hour (late 1990s); the other guys had weight-lifter builds and were on >£10 (they travelled around the country doing the same job, there wage was good money for low-skilled work at the time). I found out that the agency were being paid about £10 for me ... stood in dirty water all day, with the fall risk, the low wage, ... wasn't great. Then I had to quit because of injury after a few weeks. Knee was never the same.
That's not a filter, that's structured packing to give the water a large surface area to evaporate from.
Or possibly used as a drop catcher with spray nozzles underneath; either way the gas stream hits the surface without excess wasteful turbulence.
> In the 19th century and early 20th century, ballast was shoveled or forked, then screened by hand using portable devices.