Phytoremediation of textile effluents containing azo dye by using Phragmites australis in a vertical flow intermittent feeding constructed wetland

The VFCW was found to be suitable to treat an effluent containing an azo dye. For influent concentrations of 130 mgAO7 l−1 POD activity increased 2.1-, 4.3- and 12.9-fold for leaves, stems and roots, respectively. At 700 mgAO7 l−1, inhibition of POD activity occurred immediately, but it returned to the previous levels after only 2 days. An AO7 organic load of 21 up to 105 g COD m2 day−1, revealed non-toxicity, being expectable to achieve removals of 11 up to 67 g COD m2 day−1. Both [AO7] and TOC removal efficiencies were found to be similar (approximately 70%), which is indicative of AO7 mineralization. A 3 h cycle was found to be sufficient to degrade AO7 and a system buffering capacity from 5 to 25 min cycle−1 was demonstrated by flooding level control.