Abstract: A portable modular water air stripper system for remediation of contaminated water, such as groundwater at an outdoor contamination site, has its primary components, including the frames of a vertical assembly of individually demountable tray units, a sump and cap member, formed as hollow rotationally molded plastic pieces. Each tray unit has an air-porous sheet member having air-flow apertures with a diameter of 0.100 inches or less constructed to retain water during stripping action by air passing upwardly through the apertures. Each sheet member is removable from a respective tray frame and has mounted thereon a baffle that defines a tortuous water flow path across each tray. In one embodiment, the baffles extend between and are substantially sealed to the undersurface of the next higher tray.