The absorbance at 416 nm, related
to porphyrins, was correlated to the COD during wastewater biodegradation. The tryptophan-like/
fulvic-like fluorescence intensity ratio was related to the extent of biodegradation. The COD removal
efficiency ranged from 74% to 94% with an hydraulic retention time (HRT) of 23 h. A ratio of tryptophan-
like/fulvic-like fluorescence intensities higher than 1.2 indicated incomplete biodegradation of
the wastewater and the need to increase the HRT.