A review of dye effluents polluting African surface water: sources, impacts, physicochemical properties, and treatment methods

Abstract This review investigates the pervasive issue of dye effluent pollution in African surface waters, focusing on its significant adverse effects on both human health and environmental quality. Drawing from 63 articles published between 2004 and 2022, the review includes studies from Northern, Western, Eastern, Central, and Southern Africa, illustrating the widespread nature of dye contamination across the continent. Five primary sources of dye effluents are identified: textiles, food industries, dye producers, artisan dyes, and tannery-paint industries, all of which contribute substantially to the degradation of water quality. The physicochemical properties of dye effluents show high toxicity levels in surface waters, with significant regional variations. These variations highlight the importance of considering the specific characteristics of dye types and processing chemicals to fully understand the contamination levels. In evaluating treatment methods, the review finds that adsorption, coagulation/flocculation, filtration, and advanced oxidation processes (AOPs) such as photocatalysis, photo-Fenton oxidation, and plasma-chemical treatment are effective in mitigating dye pollution. The application of these methods varies across different African regions, indicating the need for region-specific approaches based on local conditions and available resources. The review also examines the impact of dye effluents on aquatic ecosystems and human health, with risk assessments revealing effects ranging from acute to chronic. This demonstrates the urgent need for targeted interventions to address dye effluent pollution in African surface waters, thereby protecting both environmental and public health. Graphical Abstract