Abstract: An ultra-violet wastewater disinfection system is disclosed in which wastewater flows through a treatment chamber having a plurality of tube-type ultra-violet lamps in a parallel array supported therein at an acute angle with respect to the flow of wastewater through the treatment chamber. In this configuration, the wastewater flows through the array of lamps regardless of the depth of the water in the treatment chamber. The wet/dry configuration wherein a portion of the lamps is submerged and a portion of the lamps is not submerged provides very desirable results in terms of the kill rate of fecal coliform present in wastewater.