Methylene Blue Removal and Phytotoxicity Evaluation by Aspergillus niger

Abstract

As the global population continues to grow rapidly, the textile industry, one of the most significant sectors, faces increasing challenges in treating wastewater contaminated with dyes. The widespread use of synthetic dyes in textile manufacturing has made traditional treatment methods inadequate, emphasizing the need for more advanced and sustainable cleanup strategies. Among various techniques for removing color from industrial effluents, biodegradation-based methods have gained significant attention due to their cost-effectiveness and environmentally friendly qualities.
In this study, Aspergillus niger was utilized to remove methylene blue, one of the most common dyes found in textile wastewater, through a biosorption-based remediation process. Experiments were conducted over seven days at temperatures ranging from 25 to 35 °C, using both live and dead fungal biomass, with initial dye concentrations of 10-100 mg/L. The highest removal efficiency of 88.7% was achieved on the fifth day. Under these optimal conditions, the temperature and initial dye concentration were determined to be 25 °C and 10 mg/L, respectively.
Subsequently, a phytotoxicity test was performed using green lentil (Lens culinaris) under optimized conditions. Seeds were irrigated with three different solutions: A 10 mg/L methylene blue solution, control water (tap water), and the post-biosorption treated solution. After seven days, germination rates were recorded as 90%, 100%, and 100%, respectively. The results showed that the biosorption process had no harmful effects on seed germination, indicating that the treated effluent posed no detectable phytotoxic risk.