mobile washing??? need a wash mat and a wet/dry vac...then dump into a holding tank and call the corresponding agency to come collect the water. Well, this is the correct way to do it anyway...Its funny...I see guys all the time being "ECO-friendly" and then dumping down the toilet in shops, or down the drains inside shops....its still going to the same place as street drains, thats not reclaiming the water, its re-directing so the city cant see you outside washing cars and having water all over the ground!
At the same time, driving your car produces more pollutants that land on the ground than washing a dirty car (where do you think that dirt came from in the first place) so I really cant see what the big deal is...especially when a lot of the soaps are bio-degradeable!!!