how to store the old chemicals in the doka

I received four jerrycans from the 'Klein Grof Vuil verwerking' to store our used chemicals in. Two black and two yellow ones, both written on the side what needs to go into what. I've just learned that we can't put the blix and developer together in a bottle
because they need to be seperated in order to break it down.
When we bring the chemicals away, we get new empty jerrycans from them.
I don't mind doing this from now on.
Danielle