The idea of getting some resources back from the dirty water from ore processing is nice, but the yields are way to low to be worth it, if you process 36 ore you get enough dirty water for 1 cycle. That gives you 0.1 ore. That is way to low to be worth it only to recycle the water
I guess it's set that way to prevent loops from pollution filter cleaning but that is very very low yield. To get 1 ore/s ( and 3 stone) at current yields from filters you need 20 filter plants, 160 Assembler 3 cleaning them and 13334 Air purifier.

I think that could be easily increased to I think 3.6 ore from processing 36 or something in this ball park. With that you would still need 720 Air purifier. for 1 ore/s and filtering the dirty water is actually worth it.

Filtration should be seen as the low-pollution alternative to dumping, although both still have annoying byproducts. That's good enough as it is, anything dirty water is an optional technology anyways and not needed to play the mod. It saves you the fluid handling in larger bases.

If you want free ores, Wood-->Matter-->Ore is already good enough. Old Krastorio had much better filtration ratios, but large filtration builds still fell behind non-filtration bases because of UPS constraints. The only way to make it work better right now UPS wise would be a much lower amount of fluid processed (like 5 water-->5 dirty water), significantly improved ratios and Filtration recipe speed. But even if that would increase total yield by let's say 50%, why not just boost the ore processing recipe instead? And returning so much that you can loop it would make mining redundant. You already have infinite resources via matter and multiple loops anyways, in my opinion adding another is not necessary.

Feel free to modify the recipes and try them out with different yields.

There isn't a difference between the pollution levels, both have 5 pollution/min and process 50 fluid per second and that is insignificant compared to the furnaces and chem plants anyway.

It's not about the free ore for me, it's about a somewhat complicated system that doesn't do enough to be worth it being set up. The part about the Air purifiers was more about how you could easily upgrade the recipe to 36x without giving you significant amounts of ore from Air purifiers. I think 10% additional yield would be reasonable, a lot more reasonable then 0.28% additional yield.

Not needing additional water is a plus but not a big one on my opinion, the amounts you need are not significant in any way.

I see, it's about being almost meaningless compared to dumping. I wasn't aware the Fluid burner accepted modules and beacons. This really makes both methods almost identical early on but filtration worse beyond mid-game. Apparently slapping burners on the outputs of everything dirty water is somehow more efficient. I feel so stupid now after I assumed filtration plants had the advantage of modules. I have to agree, filtering dirty water really is pointless right now.