The present invention relates to an air emission control system for removing volatile organic compounds (VOCs) and other objectionable contaminants from an emitted gas stream which is generated from a water treatment means. Specifically the improved air emission control system of this invention relates to collecting, dehumidifying, bypassing, diluting, monitoring, purifying recycling and reusing the emitted gas stream, and also relates to feeding an inert gas, upon demand, for reducing oxygen content of said emitted gas stream, in turn, for preventing a gas purification contactor from being ignited and/or exploded due to oxidation of carbonaceous substances inside said gas purification contactor. A complete water treatment and gas emission control system is developed by applying the air emission control system to either single stage water treatment or multiple stage water treatment. The present invention which causes no air pollution is a low cost and highly efficient alternative to present site remediation and water treatment technologies.
