Removal of azo dye-containing wastewater using constructed wetlands

Abstract

A constructed wetland system incorporating sequential upflow and downflow as well as anaerobic and aerobic environment can improve the treatment performance of textile wastewater for effective decolorization and biodegradation of organic compounds. Two laboratory-scale anaerobic-aerobic baffled constructed wetland (ABCW) reactors vegetated with Typha latifolia and Phragmites australis and equipped with supplementary aeration at 3 hours interval were built to examine the treatment performance of the reactors to treat synthetic wastewater and amaranth-containing synthetic wastewater. ABCW reactors achieved excellent COD reduction which was 98.2% for both vegetated with T. latifolia and P. australis. High NH4-N removal was obtained where it achieved 96.3% and 96.8% for each reactor respectively. Meanwhile, 30.4% and 30.6% of NO3-N removal were accomplished for reactors planted with T. latifolia and P. australis correspondingly. When ABCW reactor vegetated with P. australis was fed with amaranth-containing wastewater, it obtained 100% color removal. Nevertheless, the COD reduction efficiency dropped slightly to 91% which may be due to incomplete mineralization of azo dye. Therefore, supplementary aeration took significant role in controlling anaerobic and aerobic region proportion to accomplish both color removal and aromatic amines reduction. Moreover, the wetland vegetation demonstrated excellent acclimatization and reproduction when fed with both synthetic wastewater and amaranth-containing synthetic wastewater.