A NOVEL THIN-FILM PHOTOREACTOR

A novel thin film photoreactor is described and characterised. The pho toreactor was based on a nozzle of special design which generated an u nsupported thin liquid film commonly referred to as a liquid 'bell'. T he arrangement described permitted liquids to be irradiated without ma king contact with either the UV sources or any solid walls in the vici nity of the sources. High speed cine photography of air bubbles entrai ned by the liquid films enabled estimates of film velocities and thick nesses to be made. The films accelerated under the influence of gravit y with velocities in excess of 2.8 x 10(2) cm s(-1) being obtained nea r the bottom edge of the bells. Film thicknesses decreased correspondi ngly, measuring approximately 0.3 cm at the top of the bell and only 1 .0 x 10(-2) cm near the bottom. From the film thicknesses, internal an d external bell surface areas and volume could be determined: these we re respectively 2697.1 cm(2), 2705.0 cm(2) and 80.4 cm(3). A bioassay based on the bacterium Escherichia coli was used to determine the UV d ose accumulated by the bell. The doses obtained ranged from 2.03 mW-s cm(-2) for irradiation by a single source, to 4.84 mW-s cm(-2) for irr adiation by all five sources. The properties of the bell photoreactor make the unit potentially applicable to areas of photo-technology in a ddition to UV sterilisation of liquids.