A muffler for an engine in oilfield applications has a tube with nozzles in its inlet section for spraying a mist of water from the well into the exhaust gases produced by the engine, so that a significant portion of the water is converted to water vapor and exits with the exhaust gases at the outlet of the tube. Vortex generators on the interior surface of the midsection of the tube create turbulence in the exhaust gases and water mist. A sump at the outlet section of the tube collects the remaining water and pollutants trapped by the water for subsequent disposal.