An ultrapure water treatment system is provided by the present invention. e system comprises a housing, a water supply means including a water inlet and a water outlet communicating with the housing and defining a path of travel of the water from said inlet to said outlet, irradiation means for irradiating water with 185 nm UV light positioned within the housing, and a catalytic filter positioned in the path of travel of the water. The catalytic filter comprises a non-polymeric porous material having a photoactive catalyst thereon. Exemplary photoactive catalysts include TiO.sub.2, ZnO, WO.sub.3, SnO.sub.2, CU.sub.2 O, and CdSe.