UV Reactor design: a simulative approach

Ultraviolet (UV) technology is an emerging technology for drinking and waste water treatment. It can either be used as disinfection barrier, where the UV light is used to inactivate pathogenic microorganisms, or in combination with hydrogen peroxide as an advanced oxidation process. Design of UV reactors is very complex and it is difficult to predict the real treatment achieved; this is due to the difficulty in predicting the fluid dynamic phenomena and in integrating these phenomena with the UV intensity distribution. In this paper the design and optimization of UV-reactor based on computational fluid dynamics and on Multiple Point-Source Summation (MPSS) lamp emission model will be discussed. Microbial inactivation depends on the UV-C dose, described as UV-C intensity multiplied by exposure time. For UV-C dose calculation it is therefore necessary to determine the exposure time of a particular particle (i.e. a microbe) and the UV-C intensity as function of the position in the irradiation chamber. In this study we calculate the dose absorbed by different particles of water through the reactor integrating the results obtained by CFD (speed, streamlines) with the calculation of UV-C intensities obtained using the MPSS lamp emission model. We investigate how the UV-C dose changes at different flow rates and at different diameters of the reactor. With this analysis we obtained an advanced tool that allows to correlate the minimum UV-C dose required, the flow rate, the reactor geometry, the operation cost, the investment cost in order to optimize the reactor from both technical and economical point of view. The method we have used in this paper can be extended to the optimization of more complex geometries, in which we can act on many more operating parameters (number of lamps, lamps disposal, type and number of baffles, etc...).