The present invention relates to a fluid treatment system comprising: an inlet; an outlet; and a fluid treatment zone disposed between the inlet and the outlet. The fluid treatment zone has disposed therein: (i) an elongate first radiation source assembly having a first longitudinal axis, and (ii) an elongate second radiation source assembly having a second longitudinal axis. The first longitudinal axis and the second longitudinal axis are non-parallel to each other and to a direction of fluid flow through the fluid treatment zone. The present fluid treatment system has a number of advantages including: it can treat large volumes of fluid (e.g., wastewater, drinking water or the like); it requires a relatively small “footprint”; it results in a relatively lower coefficient of drag resulting in an improved hydraulic pressure loss/gradient over the length of the fluid treatment system; and it results in relatively lower (or no) forced oscillation of the radiation sources thereby obviating or mitigating of breakage of the radiation source and/or protective sleeve (if present). Other advantages are discussed in the specification.