Analysing performance of real textile wastewater bio-decolourization under different reaction environments

The biological colour removal from textile wastewater is challenging because of the toxicity of dyes tomicroorganisms, and the need to test the process on real streams in order to ensure the reliability of theproduced data. This present study has provided a comparative analysis of the bio-decolorization of a realwastewater containing a mixture of azo dyes under different environments: single aerobic and anaerobic,and sequential anaerobic-aerobic. Tests were performed in sequencing batch reactors operated atdifferent exchange ratios and colour loads in the range of 0.1e0.3 and 0.002e0.1 kgCOD m3 d1,respectively. The work cycle lasted 24 h. With reference to the dominant wavelength, l ¼ 536 nm,resulting from the influent characterization, a maximum limit value of ~30% was observed for the colourremoval in the aerobic system. Better performance has been achieved with the anaerobic (65% removal)and the sequential anaerobic-aerobic system, which reached efficiencies of 70e80%, for the range ofapplied colour loads. The sequential system exhibits the highest removal rate, which, for the highestcolour load, is equal, in terms of absorbance units to 0.043 AU d1 L1. These values are even higher thanthe process rates obtained with more complex technologies, such as the granular sludge bioreactors. Thedemonstrated high performance of the sequential process with a real wastewater is a relevant stepforward for promoting the application of the biological treatment (more sustainable than the generallyemployed chemical physical ones) to remediate highly polluted dye streams.