Mixing waste waterbornes with solvent based material can lea to gas emissions that are explosive. You will know as you can see the bubbles coming to the surface. This is caused by the reaction of product from silver colours and creation of hydrogen gas. We are not sure, but there is cause for alarm in this may have been the cause of two explosions and a death to date. Would suggest very strongly that you get good H& S information from a goverenment agency rather than just a supplier's OK. Best wishes.
I'm new to CH, so new to responding. In MN we have helped clients identify their various waste streams. We recently worked with the local sewer authority (for Minneapolis-St Paul) on disposal of water from waterborne gun cleaners (after it has gone through the filtering system). That water tested out okay for going in the sewer (we tested gun cleaners that were used with different brands of paint).
For the waterborne paint waste (so, the paint related waste), some of the paint manufacturers (in particular BASF) said do not mix at all with solvent waste. Most of our clients are mixing solvent related waste with the waterborne waste with no problem. They ship all of it as hazardous waste (but there is a lot less waste than when they used all solvent based paints).