AbstractThe process air emissions from municipal wastewater treatment plants primarily consist of hydrogen sulfide gas, along with other organo‐sulfur compounds, and some trace quantities of volatile organic compounds, and some trace quantities of volatile organic compounds (VOC). Various Federal and/or State Regulations require monitoring, and control of these emissions down to some specified levels.At the Deer Island Wastewater Treatment Plant of the Massacbusetts Water Resources Authority (MWRA), air containing hydrogen sulfide is collected and treated in several emission control systems. These systems consist of wet scrubbers which facilitate destruction of hydrogen sulfide gas and the related odor by continuously contacting the collected air counter‐currently with a strong oxidizing solution of sodium hypochlorite.This paper reviews the performance of a typical scrubber in light of the theory of absorption followed by chemical reaction. Based on an analysis of a set of test data, it has been concluded that when the concentration of hydrogen sulfide at a scrubber inlet exceeds 25 ppm, the scrubber becomes mass transfer limited. This can lead to the incomplete oxidation of hydrogen sulfide gas. Unreacted H2S eventually can exit the scrubber while partially oxidized H2S, in the form of elemental sulfur, can deposit on, and eventually foul, the packing media. Measures taken to overcome such a situation have also been repor