Just to be clear: my comment in the dichromate was motivated by Swedish environmental laws. Discharging Chromium ions in any oxidation state is illegal. Any large town will have a place you can send your collected waste, usually for free, but I don't know where that is in Göteborg. You just need to find the right 'gubbe' to ask.

FWIW, I am a physicist, was a Docent at Lund University and for many years was the Safety Officer for my Department.