Dispose of the etchant as you see fit. Some people find that they can get several "runs" out of a single batch of etchant. If so, funnel the etchant back into the container as shown here. Plastic funnels only.

If you choose to dispose of the etchant, you should do so by flushing it down the toilet. Do not pour it down your kitchen sink, as the sink as well as the plumbing is likely to be made of material that would not enjoy meeting ferric chloride.

Clean your work area and rinsing area very well.