[Frameworks] B+W Handprocessing Reversal Bleach?

[marcia connolly]

Hello all I'm teaching Experimental Film at NSCAD and we are
hand-processing in a communal darkroom and there is a concern about
our bleach. Does anyone know what the least toxic recipe for a 3374
Hicon B+W  reversal bleach is? One that does not use P. Dichromate or
Permanganate?

Has anyone tried a Potassium Ferricynide based bleach?

Any help would be appreciated.

Marcia Connolly