A storm water treatment device that is installed under the grate of new or existing catch basins, and more commonly referred to as an insert. The catch basin decontamination apparatus has a universal housing and support ring that allows one design to fit most applications. Adjustable chains allow for proper position below grate and a semi-flexible molded or rigid deflector directs incoming drain water to the housing. A slip-on filter/absorber cartridge fits over a perforated drain tube, in the center of the housing, allowing the drain water to first pass through the filter/absorber media before exiting through the drain tube and out the bottom of the housing. The filter/absorber cartridge includes a variety of absorber materials that absorb oil and repel water. Activated carbon, microbes and other site specific absorbents can be used in the replaceable slip-on cartridge. A leaf pre-strainer helps prevent leaves and debris from entering the housing. A clean in place suction tube and clod buster form of the apparatus aids in cleaning the housing.