Soluble bio-organic substances (SBO) isolated from urban biorefuses have been investigated in photocatalytic processes for wastewater treatment using a cationic dye, namely crystal violet (CV) as target compound. The SBO have been found to enhance the photobleaching of CV solutions with an optimal SBO concentration of ca. 20 mg L-1. Mechanistic investigation based on chemical probes and changes in the absorption spectrum of CV in the presence of SBO seems to indicate that a complex formed between sensitizer and substrate plays a major role in the process. SBO have also been tested for the implementation of photo-Fenton processes at circumneutral media: the observed pseudo first order rate constants for CV decoloration was higher for UV/SBO/Fe(II)/H2O2 (5.5 x 10(-3) min(-1)) than for UV/Fe(II)/H2O2 (1.5 x 10(-3) min(-1)). A modified mechanism, in which HO center dot are less relevant that at the acidic medium, is in agreement with results of experiments carried out with chemical probes. (C) 2012 Elsevier B.V. All rights reserved.