A treatment system for remediating some forms of sulfur, CO2, and other contaminants/impurities from a gas stream includes at least one of a process vessel and a treatment coil. Each of the vessel and treatment coil have internals, different in design from each other, which promote intimate mixing and extended contact time between a treatment composition and a gas being treated. The vessel, which additionally facilitates vapor/liquid separation, operates about one-half to two-thirds full of liquid treatment composition. In some embodiments, the treatment coil is a serpentine arrangement of piping, into which the atomized treatment composition is injected on a continuous basis.