Jet mixing is a device which is used to homogenize liquids in short operating times. In this work, a pilot scale photo-reactor, equipped with two internal mixing jets and two immersed UV-C lamps (each with incident photon flux of 6.1 x 10(-6) einstein/s) was used for discoloration and aromatic degradation of 30 mg/L of Direct Red 23, as a model pollutant in water, by UV/H2O2 process. Effects of physical and chemical parameters were investigated, and optimum conditions were obtained as: nozzles diameter of 1.6 mm, nozzles direction angle of 45(-) directed to the walls of the reactor, flow-rate of 1.7 L/min, initial H2O2 concentration of about 200 mg/L and natural initial pH of 6.6. Under these conditions 96% discoloration and 86% aromatic degradation efficiencies were obtained after 60 min treatment. Furthermore, the kinetic investigation revealed pseudo-first order reactions for discoloration with different H2O2 initial concentrations. Accordingly, as a figure-of-merit, the "electrical energy per order" was determined within 2.44-6.04 kWh/m(3)/order, showing promising low electrical energy consumption and high economical benefit in comparison with similar treating photo-reactors. (C) 2011 Elsevier B.V. All rights reserved.