Abstract
The release of untreated dye textile wastewater into receiving streams is unacceptable
not only for aesthetic reasons and its negative impacts on aquatic life, but also
because numerous of dyes are toxic and carcinogenic to humans. Strategies as of now
used for treating textile wastewaters have technical and economical restrictions. The
greater part of the physico-chemical methods, which are used to treat this kind of
wastewater, are costly, produce large amounts of sludge and are wasteful concerning
some soluble dyes. In contrast, biological treatment such as constructed wetlands are
cheaper than the traditional methods, environmentally friendly and do not produce
large amounts of sludge. Synthetic wastewater containing Acid Blue 113 (AB113) and
Basic Red 46 (BR46) have been added to laboratory-scale vertical-flow construction
wetland systems, which have been planted with Phragmites australis (Cav.) Trin. ex
Steud (common reed). The concentrations 7 and 208 mg/l were applied for each dye at
the hydraulic contact times of 48 and 96 h. Concerning the low concentrations of BR46
and AB113, the unplanted wetlands are associated with significant (ρ<0.05) reduction
performances, if compared with planted wetlands concerning the removal of dyes. For
the high concentrations of AB113, BR46 and a mixture of both of them, wetlands with
long contact times were significantly (ρ<0.05) better than wetlands that had short
contact times in terms of dye, colour and COD reductions. Regarding nitrate-nitrogen
(NO3-N), the reduction percentage rates of AB113, BR46 and a mixture dye of both of
them were between 85 and 100%. For low and high inflow dye concentrations, best
removals were generally recorded for spring and summer, respectively.