the tubular housing that is rectangular trapezoidal square triangular etc in cross section it is also envisioned that the uv lamp source 214 is relatively shorter so that one or more of the inward features 230 232 234 only functions to increase duration of the fluid but does not impact relative closeness to the uv lamp source 214 by minimizing the production of low dose fluid elements using one or more of the elements 230 232 234 it has been demonstrated by proven computational fluid dynamics and numerical methods to increase disinfection efficacy of the uv treatment zone 202 by 15 as measured by net log reduction of virtual microorganisms using the same energy input this increased efficiency has been shown to be more pronounced with relatively short chambers and or chambers with relatively large diameters therefore another benefit of the present invention is to enable more effective compact uv treatment chambers it will be appreciated by those of ordinary skill in the pertinent art that the functions of several elements may in alternative embodiments be carried out by fewer elements or a single element similarly in some embodiments any functional element may perform fewer or different operations than those described with respect to the illustrated embodiment also functional elements e g modules databases interfaces computers servers and the like.