Algal Treatment of Textile Dyehouse Wastewater

In this study, treatment of mono-azo dye, Tectilon Yellow 2G (TY2G), and di-azo dye, Erionyl Navy R (ENR), using an algal species, Chlorella vulgaris, was investigated. In an attempt to conduct a treatability study for TY2G by C. vulgaris, different concentrations of TY2G were added to the reactors containing initially about 500 mg/m3 algae in terms of Chl-a content. The COD removal efficiencies were determined as 69.1, 65.8 and 63% for the initial TY2G concentrations of 50, 200 and 400 mg/L, respectively. Acclimation of C. vulgaris to TY2G caused these removal efficiencies to increase to 88, 86 and 80% for ascending dye concentration. The main mechanism of the removal was determined to be degradation and an end product, aniline, formation was observed as confirmed by HPLC analysis. Initial algae concentration was found to be important both in terms of COD removal achievement and contact time requirement. In an attempt to test toxicity of the treated dye effluent, as compared to dye itself, toxicity experiments using activated sludge biomass were performed. By comparing the specific growth rates (μ) values of activated sludge biomass obtained in these two sets, it could be said that toxicity of end product formed after algal treatment of TY2G were less than that of the dye itself. Removal in COD and A220nm occurs during the exponential growth phase of C. vulgaris indicating a growth-associated treatment and hence, mixotrophic growth of C. vulgaris.