I suggest to sterilize your carbon in an Autoclave and eventually pass your feed stream trough UV before entering the Adsorption unit.

I'm not sure if I understand your question.  Nitrification and denitrification are bacterially mediated processes.  If your goal is to isolate/eliminate those processes to focus on chemical reactions, you simply need to mix inert standards.  I don't recommend autoclaving your standards once they're mixed, since the heat will influence them, but certainly you could autoclave or boil the RO/DI water you're using to make the standards before you make them.  Generally the impact of nitrification/denitrification on standards in a bottle is pretty low.  Those solutions tend to be shelf stable for 1 year or so without additional precautions beyond standard good lab hygiene.

thank you