The disclosed principles employ a UV reactor design for photo-based treatment of contaminated fluid media using a concentric single light source/single sleeve design, with multiple such concentric light source/sleeve units placed in parallel. In one embodiment, such a reactor may comprise an inlet manifold and an outlet manifold, and a plurality of tubular chambers connecting the inlet manifold to the outlet manifold. A plurality of such irradiating units are located within corresponding ones of the tubular chambers such that a fluid path is provided between each of the transparent sleeves and its corresponding tubular chamber where the contaminated fluid is irradiated as it passes through the chambers. The inlet ends of all of the chambers are connected to a single fluid intake manifold. This design allows the contaminated fluid pressure and flow to be evenly distributed among all of the fluid chambers via the intake manifold.
