Mobile treatment systems and methods for use in removing hydrogen sulfide from oilfield effluents. The systems and methods use a pre-treatment subsystem, a vapor treatment subsystem and a treatment subsystem interconnected by a plurality of piping and valve subsystems. The systems and methods are not dependent on pH and may operate at temperatures as low as −20° C. The systems are easily transported to, and readily assembled at a site and are inexpensive, simple, quick, and extremely effective at removing large-scale quantities of hydrogen sulfide from oilfield effluents.