a and 1b the liquid has a flow path whereby it enters through input 12 passes upwardly through chamber 22 over top surface 26 of wall 20 and downwardly through chamber 24 before exiting at outlet conduit 14 the inputs and outlets are shown here as cylindrical tubes but the configurations could have other geometries including funnel shapes or with multiple conduits or could include a single conduit that fans out to provide water along a slot so that it is more evenly distributed along the width of chamber 22 wall 20 has uv transparent sides 20 a and 20 b and encloses one or more uv lamps 32 lamps 32 can have one of several different configurations or combinations of configurations including linear lamps spiral lamps or serpentine lamps including u shaped configurations inwardly facing surfaces 16 a and 18 a of walls 16 and 18 respectively are preferably but need not be designed to reflect uv light so that light energy from lamps 32 passes through the water in chambers 22 24 and is further reflected back to provide additional uv energy to the water for disinfection or decontamination one or more of walls 16 18 and 20 can be movable relative to other walls to alter the depth of chambers 22 and or 24 to control the depth or u201c thickness u201d of the flow path the depth of the flow path incorporates certain tradeoffs a deeper.