Beyond Decolorization: Critical Evaluation of Color Monitoring Methods in Advanced Textile Wastewater Treatment: A Review

Color removal from dyehouse effluents remains a persistent and largely unresolved challenge, as a decoloration technique that is both economically viable and consistently effective, has not yet been established at full scale. In parallel, the determination of color as a key regulatory and performance parameter still lacks a standardized, sensitive, and practically convenient measurement approach. This review examines the commonly adopted methods and analytical tools used to monitor and assess color removal from dyehouse effluents and textile industry wastewaters treated by heterogeneous advanced oxidation processes (AOPs). An evaluation of recent experimental studies shows that color removal is predominantly quantified in terms of apparent and true color, employing diverse visual comparison techniques, spectrometric analyses, and colorimetric indices before, during, and after oxidative treatment. The pronounced variability in analytical practices not only undermines direct comparison of reported treatment efficiencies but also introduces uncertainty in regulatory compliance assessment. These limitations clearly highlight a critical research gap and underscore the urgent need for harmonized, robust color measurement protocols to enable reliable evaluation and practical implementation of AOP‐based decoloration technologies.