Assessment of the biodegradability of a monosulfonated azo dye and aromatic amines

Biodecolourisation of an azo dye by anaerobic cultures using, a liposomal textile levelling agent as primary substrate was assessed. Liposomes seem to facilitate the uptake of the dye (Acid Orange 7) by anaerobic biomass, leading to a fast decolourisation (colour removal of 96% was achieved in the first sample port of the reactor profiles). Oil the other hand, the presence of dye (60-300 mg l(-1)) caused it decrease in the chemical oxygen demand (COD) degradation rate (4.1-2.5 g COD removed l(-1) d(-1) for 60 and 300 mg l(-1) of dye, respectively), suggesting inhibitory effects. Aerobic degradation of aromatic amines was investigated in aerobic respirometric assays with different types of inocula. Sulfanilic acid and aniline were mineralised by inocula with a significant microbiological diversity, even with domestic effluent. These results were confirmed by a significant reduction of COD, total organic carbon (TOC) and a high oxygen consumption (biochemical oxygen demand/theoretical oxygen demand), 92 +/- 4%. Kinetic analysis showed that a sigmoid function describes quite well the experimental data, even better than the exponential model. Orthanilic and metanilic acids and 1-amino-2-naphtol were persistent under the tested conditions. (C) 2007 Elsevier Ltd. All rights reserved.