I’ve used buildcraft’s floodgate to release water into a reservoir. I’m toying with the idea of turning on finite water and recycling water from it. I’m guessing you could do the same with sluice juice and pump your waste water back out, flooding the overworld dwarf fortress style.
In terms of pollution I’ve found that Gregtech makes it’s own, as built up areas suffer from terrible lag pollution. 
I have wanted to add pollution aspects to industry though, kind of like thaumcraft’s taint spreading through the land. In built up areas you would find that leaves die off, grass becomes greyer, plants have trouble growing and water becomes non-potable.