Biodegradation and Detoxification of Distillery Spent Wash by Aspergillus niger and Pseudomonas fluorescens

Distillery spent wash (DSW) is a highly polluted industrial effluent requiring effective and eco-friendly treatment strategies. An experiment was conducted during 2024–25 at the Soil and Water Management Research Unit, Navsari Agricultural University (NAU), Navsari, to evaluate the efficiency of microbial inoculants in the degradation and detoxification of distillery spent wash using a Completely Randomized Design with Factorial Concepts along with three microbial treatments-M0 (no inoculation), M1 (Aspergillus niger at 1 g/L) and M2 (Pseudomonas fluorescens at 10 mL/L) and five replications. Results indicated that microbial inoculation significantly reduced organic pollution parameters and treatment efficiency increased with incubation time. Among the treatments, M2 recorded the lowest mean values of chemical oxygen demand, biochemical oxygen demand, total solids and total dissolved solids. The interaction M2D3 (30 days incubation) was the most effective, achieved maximum reduction in chemical oxygen demand, biochemical oxygen demand and total solids contents, indicated a strong synergistic effect of microbial inoculation and extended incubation. M2 also showed the highest reduction in optical density across all tested distillery spent wash concentrations, even at 10th day of incubation. In contrast, M1 was more effective in removal of micronutrient, particularly iron, manganese, zinc and copper, with the lowest concentrations observed under the M1D1 interaction. Overall, Pseudomonas fluorescens with extended incubation was optimal for organic pollution reduction, while Aspergillus niger was more effective for micronutrient removal, demonstrated that an integrated microbial approach is an efficient and eco-friendly strategy for distillery spent wash treatment.