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

摘要

An azo dye,acid orange 7 (AO7),was selected to study the role of Phragmites australis (P.australis) peroxidases (POD) activity in its degradation in a vertical flow constructed wetland (VFCW).Crude plant extract was found to degrade AO7 and its aromatic amines,after 120h in contact with H_2O_2,and removals of 3.2-5.7 mg_(AO7) g_(P.australis)~(-1) were obtained for 40 mg_(AO7) l~(-1) (8 mg_(AO7) g_(P.australis)~(-1)). The VFCW was found to be suitable to treat an effluent containing an azo dye.For influent concentrations of 130 mg_(AO7) l~(-1) POD activity increased 2.1-,4.3- and 12.9-fold for leaves,stems and roots,respectively.At 700 mg_(AO7) 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 m~2 day~(-1),revealed non-toxicity,being expectable to achieve removals of 11 up to 67 g COD m~2 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.