Removing Acrylic Paint From Rinse Water
I dissolved 1/2 a tablespoon of aluminum sulfate in a few ounces of water, before adding that to the rinse water.
Then I added 3/4 of a tablespoon of hydrated lime into the rinse water.
After letting it sit for awhile, it went from being a solid green, to looking like the image on the top left. Where the paint separates from the water and settles to the bottom of the jug.
At this point, I tested the pH of the clear water to make sure that it was between 5 and 9. It was around 7.
Then I put two bamboo coffee filters (I chose bamboo because it is sustainable) into a metal funnel, and put the metal funnel into another jug. The bottom left photo shows the paint staying in the filter, with clear water in the jug below. It takes awhile of pouring a little bit from the dirty water jug into the filters. After sitting over night, the water has completely drained from the filters. We are left with the final image with the cracked paint in the filter and the clear water in the jug. The water is supposedly safe to pour down the drain at this point!
I got these instructions from Golden paint.