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Photocatalytic Decolorization of Reclaimed Water Using Photocatalyst Coated Black Light with Spiral Fluid Flow System

Abstract We designed and assembled a photocatalyst module for water treatment (referred to hereafter as module-I). The module consists of a Pyrex cylindrical tube into which a photocatalyst coated black light (P-BL) tube was inserted, and the admission port for water is attached tangentially to the curved surface of the P-BL tube. The decomposition-rate constant that we obtained by using a 3-ppm methylene blue aqueous solution showed a drastic increase when the fluid velocity exceeded 2 L/min. We think that the fluid velocity of 2 L/min is the turning point at which the flow pattern changes from a laminar flow to a spiral flow turning around the P-BL. We found that module-I is also effective for decomposition of 50 ppb or less concentration levels of dissolved substances such as 4,4'- (1-Methylethylidene)-bisphenol. From the results of decolorization experiments conducted with module-I in which we used 1 L of amber colored reclaimed water (RW) from a circulation toilet system as real waste fluid, we found that RW became transparent within 2-hours of operation at the fluid velocity of 6.1 L/min.