Hello; I have been dumping the water from my tanks on to potted plants and into my lawn for a long time. It seems to help.
I also noted since moving to my current home that the area of the lawn around the septic field lines does grow much thicker grass. When we had almost no rain and very high tempratures around here in June and July, that area was the only place where I had any green grass. I suppose part of that was the additional moisture at that period, but the grass ia always thicker here at all other times.