Decolorization of dyestuffs by some species of green algae and cyanobacteria and its consortium

Abstract

Synthetic dyes are scattered in untreated or inappropriately treated effluents, and their dangerous items created during the halfway corruption are released into the water bodies that cause a horrendous smell, which prompts anomalous changes in the nature of water. In the present study, green algae and cyanobacteria are considered as a significant hotspot for decolorizing color and material gushing. Chlorococcum sp., Scenedesmus obliquus, Chlorella vulgaris, and Oscillatoria sp. were investigated for degradation and removal of some azo dyes [Reactive Orange 122 (Orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)]. The results showed that the maximum decolorization was spotted at 20 ppm Reactive Orange 122 with Oscillatoria sp. mixed with S. obliquus (98.54%). 20 ppm Reactive Red 194 was decolorized by Oscillatoria sp. mixed with S. obliquus (97.58%) after 7 days of incubation. The decolorization was detected by spectroscopic analysis and Fourier transformed infrared (FTIR) spectroscopy. The suitable factors that accelerated the azo dye decolorization and enhanced the biological treatment methods to be more effective and speedier in decolorization were investigated. At 25 °C and continuous lighting, the highest percentage of the azo dye decolorization was obtained; BG11 was the suitable medium that gives a high percentage of the azo dye decolorization. However, relative to the effect pH on azo dye decolorization, results show pH 11 and pH 9 more effective on azo dye decolorization for Reactive Orange 122 and Reactive Red 194, respectively. A total of 6% of thiamine and ascorbic acid recorded maximum degradation activity at Reactive Orange 122 when treated with Oscillatoria sp. mixed with S. obliquus 79.13% and 77.18%, respectively.