Reduced-pressure (vacuum) evaporation/drying of 15 liters of aqueous solution I have 15 liters of aqueous solution inside an aluminum stock pot which rests upon a hot plate. I want to reduce the boiling point from 150°C to 100°C using reduced pressure.

What is the most economical way efficiently to dry the solute? Economical means does not require specialty equipment (i.e., laboratory vacuum pumps, expensive cold traps, etc.)? 

I own a water aspirator pump (attaches to sink, 27.4 in Hg maximum vacuum, 6 liters/minute) and a 2-stage electric vacuum pump (15-micron, 3CFM) that I use for degassing epoxies. I don't know whether either of these will be of any use here.
The aspirator pump would be unlikely to be damaged by the distillate (and can be cheaply repaired or replaced), but the electric vacuum pump likely will require a cold-trap to prevent the vapors from destroying it.

The aspirator pump would seem the way to go, but you must factor in the cost of water in your location. This Nalgene aspirator uses ~6.5 liter/minute. A recirculating aspirator pump might be the best compromise for a production environment, where efficiency is important, and it might be feasible to save and recycle the distillate.