Proper disposal of steel-fx and using in driveway

[Metriccar]

I have been using steel fx in an industrial complex, using 1 gallon water bottles to neutralize it. What's happening is I have residue leading all the way to a storm drain. I am not sure if this is rust or the patinas that I am using. But even after rains it is still there.

I want to start using it in my driveway-where I will have access to a water hose. But is it going to stain my driveway? Should I be containing this somehow and disposing somewhere?

I am considering going to the gels instead because of this.