I never worried too much about dumping my dirty acrylic rinse water down the drain until we purchased a home with a septic system. I asked our septic guy if it was safe to discard it down the drain and he wasn't sure that would be a very good idea. I did some searching online and came across some methods that involve allowing the water to evaporate and then straining the sludge through a nylon stocking. That would never work for me! I paint often and use lots of water...it would take forever to evaporate, not to mention all the buckets sitting around in my studio. Other methods involve pouring the water into a bucketful of sand and letting it evaporate.
Again, not a useful idea for me.
I found that Golden Paints has the very best, ecologically friendly solution for waste water disposal.
I don't use the PH test papers anymore, because I have learned that 1 tablespoon of the Hydrated Lime and Aluminum Sulfate is enough to clear a big Lowes bucketful of waste water. It's amazing to watch the sediments coagulate and settle to the bottom of the bucket and the clean water rise to the top...almost like magic! After straining the sediment through the 12 cup coffee filters, I pour out the clean water on a plant that lives outside my studio door. I think it likes the extra boost of fertilizer!
Here are a couple of pictures of my own "disposal station".
If you like this tip, please share it with your artist friends and let me know if this works for you!