Aromatic Amine Degradation in a UASB/CSTR Sequential System Treating Congo Red Dye

摘要

In this study an anaerobic (upflow anaerobic sludge blanket reactor)/aerobic (completely stirred tank reactor) sequential system was used to treat a synthetic wastewater with minerals and co-substrate together with 100-4000 mg L~(-1) of Congo Red dye (Direct red 28) (CR), which is a banned azo dye in Turkey. The effect of hydraulic retention time (HRT) on the decolorization and the COD removal efficiency was investigated at constant 100 mg L~(-1) Congo Red concentration. 77% of COD and 95% of color was removed at a HRT of 0.486 days and a maximum organic loading rate of 6.656 kg COD m~(-3) day~(-1) in the anaerobic/aerobic stage. In the continuous operations, 88% of COD, 99% of color and 91% of total aromatic amine (TAA) were removed at a HRT of 3.60 days and at a CR concentration of 4000 mg L~(-1). This corresponds to an organic loading rate of 1.81 kgCOD m~(-3)day~(-1), and a CR dye loading rate of 46.37 g dye m~(-3)h~(-1), respectively, in the whole system. The TAA produced under anaerobic conditions was ultimately removed in the aerobic stage, resulting in very low aromatic amine recoveries (5-18%) in the last one. Therefore the aerobic effluents exhibited higher IC_(50) and specific methanogenic activities (SMA) compared to anaerobic and dye containing samples, indicating the reduced toxicity.