Biodegradation, Physicochemical Reduction, and Decolorization of Textile Wastewater Using Indigenous Bacterial Isolates

Textile wastewater constitutes a major environmental concern due to its high pollutant load, toxicity, and persistent coloration. This study evaluated the biodegradation efficiency and biotreatment potential of indigenous bacterial isolates for textile wastewater remediation. Wastewater samples were collected from textile industry discharge outlets and wastewater retention ponds in Sharada Industrial Estate, Kano State, Nigeria. The collected samples were subjected to physicochemical and bacteriological analyses, while bacterial isolates were characterized using morphological, biochemical, and molecular techniques. Dye degradation efficiency and GC-MS profiling were carried out before and after bacterial treatment to assess pollutant transformation and decolorization potential. The bacterial isolates identified were Bacillus tequilensis, Lactobacillus delbrueckii, and Klebsiella pneumoniae with the 16S rRNA gene sequencing method confirming the identities of the isolates with sequence similarities ranging from 98.30% to 99.09%. Biotreatment resulted in reductions in several physicochemical parameters, including pH, total dissolved solids (TDS), ammonia, and heavy metal concentrations. Treatment with Lactobacillus delbrueckii reduced pH from 11.4 to 9.23, TDS from 11,479 mg/L to 6,090 mg/L (46.9% reduction), and ammonia from 5.354 mg/L to 0.03 mg/L (99.4% reduction). Significant reductions (p < 0.05) were observed across most treatment groups compared with untreated controls. Decolorization studies showed progressive reductions in dye concentrations over a 15-day treatment period. Several treatment groups achieved more than 70% dye removal efficiency. 70–80% decolourisation efficiency was recorded for both malachite green and rhodamine B. GC-MS analysis further revealed biodegradation of dye-related compounds and the formation of intermediate metabolites during treatment. The findings of the study show the potential of indigenous bacterial isolates for textile wastewater bioremediation; however, further optimization is required to achieve complete mineralization and improved reduction of COD and BOD levels.