Hello Andre, I do not have ...

Hello Andre, I do not have direct experience with this, but since sodium meta bisulphite is a strong reducing agent, it acts as a disinfectant and a oxygen scavenger, neither properties being helpful in an activated sludge process.  The disinfectant properties may also be detrimental to an anaerobic reactor where the microbes are more sensitive.  In terms of precautions - it depends on the concentration in the industrial effluent, but the aim would be to oxidise with an oxidant before treatment.  This may be a challenge as there are possibly a number of other constituents that will react to the applied oxidant, and in addition oxidising sodium meta bisulphite is likely to generate SO2 which is a pungent aesthetically unpleasant odour.  Oxidants you could consider are oxygen, chlorine, hydrogen peroxide.  Hope this helps