Impact of textile dyes on human health and bioremediation of textile industry effluent using microorganisms: current status and future prospects.

Environmental contamination brought on by the discharge of wastewater from textile industries is a growing concern on a global scale. Textile industries produce a huge quantity of effluents containing a myriad of chemicals, mostly dyes. The discharge of such effluents into the aquatic environment results in pollution that adversely affects aquatic organisms. Synthetic dyes are complex aromatic chemical structures with carcinogenic and mutagenic properties in addition to high biological oxygen demand (BOD) and chemical oxygen demand (COD). This complex aromatic structure resists degradation by conventional techniques. The bioremediation approach is the biological clean-up of toxic contaminants from industrial effluents. Biological treatment methods produce less or no sludge and are cost-effective, efficient, and eco-friendly. Microorganisms, mostly microalgae and bacteria, and, in some instances, fungi, yeast, and enzymes decolorize textile dye compounds into simple, non-toxic chemical compounds. Following a thorough review of the literature, we are persuaded that microalgae and bacteria might be one of the potential decolorizing agents substituting for most other biological organisms in wastewater treatment. This article presents extensive literature information on textile dyes, their classification, the toxicity of dyes, and the bioremediation of toxic textile industry effluent utilizing microalgae and bacteria. Additionally, it combines data on factors influencing textile dye bioremediation, and a few suggestions for future research are proposed.

Eco-toxicological effect of a commercial dye Rhodamine B on freshwater microalgae Chlorella vulgaris.

In this study, the acute toxicity effects of a fluorescent xanthene dye, Rhodamine B (RhB), widely used in textile, paper, and leather industries was investigated on a freshwater microalgae Chlorella vulgaris. The acute toxicity of RhB on C. vulgaris was determined by examining the growth, cell morphology, pigment production, protein content, and the activities of oxidative stress enzymes. Based on the results of the toxicity study of 24-96 h, the median inhibitory concentration (IC50) values ranged from 69.94 to 31.29 mg L-1. The growth of C. vulgaris was conspicuously inhibited by RhB exposure, and the cell surfaces appeared to be seriously shrunk in SEM analysis. The growth of C. vulgaris was hindered after exposure to graded concentrations (10-50 mg L-1) of RhB. A significant reduction in growth rate, pigment synthesis (chlorophyll a, chlorophyll b, and carotenoid), and protein content was recorded in a dose-dependent manner. After 96 h exposure of C. vulgaris to 50 mg L-1 RhB, chlorophyll a, chlorophyll b, carotenoids, and protein contents were reduced by 71.59, 74.90, 65.84, and 74.20%, respectively. The activities of the antioxidant enzymes peroxidase (POD), and catalase (CAT) also increased markedly in the presence of RhB. A notable effect was observed on oxidative enzymes catalase and peroxidase, indicating that oxidative stress may be the primary factor in the inhibition of growth and pigment synthesis. Consequently, the experimental acute toxicity data were compared to the QSAR prediction made by the ECOSAR programme. Results showed that the experimental acute toxicity values were 67.74-fold lower than the ECOSAR predicted values. The study provides convincing evidence for the metabolic disruption in the ubiquitous microalgae C. vulgaris due to the RhB dye toxicity.