check with your local waste water treatment plant and take the msd's for any product you use.they will either give you permission to dump into sanitary sewer systems or their location or you can check with state to dump in open areas not near water ways.not sure who to ask for at the state level.
here in michigan you can get a permit to dump in a certain location like your own yard for example but your suppose to get a permit.
or you can just dump where ever and hope you dont get a ticket.most guys just run a hose off theyre dumpout somewhere in the yard of the place your cleaning.usually not a big deal.
When You get home wash your van with the waste water , the dog hair ,just drive fast to air dry and the hair clumps and foam will fly like snow flakes. Or water the plants ,isnt there fertlizer in some chems?