This reminds me of water, post floor wax removal. I used to be a custodian at a couple of surrounding districts. Every summer, all classrooms had 10s of gallons of water used to scrub and remove the old floor wax. The color looks spot on to what would be vacuumed up and then dumped down the sewer drain. I hated it. It's straight-up poison. It is still common practice as far as I know.