effluent from water softener

When you recharge the softener it recharges the media with sodium and chloride ions. When you run hard water through it, the calcium and magnesium ions bind with the chloride, and the sodium ions pass into the water (which is not really good to drink due to the sodium). The next time it recharges, the calcium chloride and magnesium chloride (other forms of salt) are flushed out, along with some brine during the brine and slow rinse cycles.

A quick google search for "salt water softening process" found numerous links including

"Frank Thompson" wrote

Very diluted brine, and Idon't know of any vegetation found around a house that will survive.

Gary Quality Water Associates

"Tom J" wrote

In some areas that, or the septic tank, is not allowed. I some areas neither are dry wells but the sewer or septic is. It's a local thingy.

Gary Quality Water Associates