The separator (contact) water belonging to one Santa Clara County California cleaners, was found so safe that the local environmental regulatory agency declared it could be disposed of through a standard sewer system. The business owner, however, had to first prove that the water was, indeed, harmless to the environment.

The company sought the help of a testing lab, whose analysis of collected water samples proved the discarded water to be safe. The lab used rainbow trout to help determine the solvent’s non-toxicity, observing how long the fish could live in the substance. It took about six months to prove the cleaner’s case to the government’s satisfaction, and in the end they were successful.