Removal of azo dye in innovative constructed wetlands: Influence of iron scrap and sulfate reducing bacterial enrichment

The research work reported here is about an innovative way of designing constructed wetlands (CW) for high removal rate of pollutants and to make them less land intensive. Influence of iron scrap (IS) and sulfate reducing bacterial enrichment (SRB) was studied in Canna indica planted CW microcosms. This is the first ever report which deals with such interaction for enhancing the performance of CW. Four sets of experiments were performed: first with normal-CW microcosm; second with SRB enriched CW microcosm; third with SRB and IS enriched, CW microcosm; and fourth with SRB and copper doped IS enriched CW microcosm. The microcosms were tested for color removal of methyl orange dye from synthetic wastewater. The SRB enriched CW achieved highest removal (99.5, 98.53, 97.05, 94.62, and 96.52%) and the normal-CW achieved lowest removal (93, 89.18, 48.72, 50.14, and 52.34%) from wastewater containing 500, 1000, 1500, 2000 and 2500 mgl(-1) dye respectively. Higher removal was achieved in SRB and IS enriched CW in comparison to other CW microcosms. At higher concentrations, enhancement in performance of SRB and SRB-IS enriched CW over normal CW was clearly achieved which was not observed in lower concentrations. During treatment of 2500 mgl(-1) dye containing wastewater, it was observed that the dye removal percentage was 37.02 higher in SRB-CW over normal-CW and 19.48% higher in SRB-IS-CW over SRB-CW in 24 h of contact time. These results clearly revealed that higher removal rate of color of dye can be achieved in innovative constructed wetlands. (C) 2012 Elsevier B.V. All rights reserved.