Biodegradation of textile wastewater: Enhancement of biodegradability via the addition of co-substrates followed by phytotoxicity analysis of the effluent

Abstract

This work reports on the biodegradation of textile wastewater by three alternative microbial treatments. A bacterial consortium, isolated from a dyeing factory, showed significant efficacy in decolourizing wastewater (77.6 ± 3.0%); the decolourization rate was 5.80 ± 0.31 mg of azo dye·L 1 ·h 1 , without the addition of an ancillary carbon source (W). The degradation was 52% (measured as COD removal) and the products of the treatment showed low biodegradability (COD/BOD 5 ¼ 4.2). When glucose was added to the wastewater, (W þ G): the decolourization efficiency increased to 87.24 ± 2.5% and the decolourization rate significantly improved (25.67 ± 3.62 mg·L 1 ·h 1 ), although the COD removal efficiency was only 44%. Finally, the addition of starch (W þ S) showed both a similar decolourization rate and efficiency to the W treatment, but a higher COD removal efficiency (72%). In addition, the biodegradability of the treated wastewater was considerably improved (COD/BOD 5 ¼ 1.2) when starch was present. The toxicity of the degradation products was tested on Lactuca sativa seeds. In all treatments, toxicity was reduced with respect to the untreated wastewater. The W þ S treatment gave the best performance.