Residual blood
was the main source of organic matter in the wastewater samples. 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.