Treatment of Textile Wastewater by Advanced Oxidation Process: Effects of pH and Oxidant Dosage

Textile wastewater has high color intensity, a high organic load, and recalcitrant pollutants, making it hard to treat by conventional methods. This study explored Fenton- based Advanced Oxidation Process (AOP) using hydrogen peroxide (H2O2) and iron catalysts to treat textile wastewater, focusing particularly on how pH and oxidant dosage influence degradation efficiency. The raw wastewater matrix exhibited severe initial contamination, featuring a color intensity of 1250 ± 45 Pt-Co units, chemical oxygen demand (COD) of 1480 ± 52 mg/L, and biochemical oxygen demand (BOD₅) of 320 ± 18 mg/L, yielding a highly non-biodegradable BOD₅/COD ratio of 0.216. Experiments were carried out at pH 3, 5, 7, and 9, and with oxidant dosages ranging from 100 to 500 mg/L. Two-Way Analysis of Variance (ANOVA) with replication confirmed that both pH and oxidant dosage exerted a statistically dominant influence on pollutant removal (p < 0.001), while a significant cross-factor interaction (F = 4.96 for COD; F = 15.13 for Color) established a powerful operational synergy between acidity and peroxide concentration. Oxidation efficiency depended strongly on pH and oxidant concentration. The best performance occurred in acidic conditions, with the highest pollutant degradation at pH 3. An optimum oxidant dosage of 300 mg/L removed color by 92%, and reduced COD and BOD by 78% and 64% at 60 minutes. Lower dosages led to incomplete oxidation; higher dosages gave little extra benefit and reduced cost-effectiveness. This Performance plateau at higher concentrations mathematically confirms a system-wide chemical deactivation mechanism driven by parasitic radical scavenging (OH + H₂O₂ → HO₂ + H₂O), wherein excess oxidant acts as a scavenger for highly reactive hydroxyl radicals. Thus, optimizing pH and oxidant levels maximizes efficiency and economic feasibility for AOP-based treatment of textile wastewater.