Long–term natural remediation process in textile dye–polluted river sediment driven by bacterial community changes

• Published in: Water research (Oxford) 2016-09, Vol.100, p.458-465
• Main Authors: Ito, Tsukasa, Adachi, Yusuke, Yamanashi, Yu, Shimada, Yosuke
• Format: Article
• Language: English
• Subjects: Amines; Aromatic amine; Azo dye; Bacteria; Coloring Agents; Degradation; Dyeing; Dyes; Freshwater; Organic Chemicals; River sediment; River sediment bacteria; Rivers; Sediments; Textile dyeing wastewater; Textile Industry; Textiles; Waste Water
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2016.05.050

The textile and dyeing industries are major sources of environmental water pollution all over the world. The textile wastewater effluents discharged into rivers often appear dark red-purple in color due to azo dyes, which can be transformed into carcinogenic aromatic amines. The chemicals used in dyeing are not readily degraded in nature and thus precipitate in river sediment. However, little is known about how dyeing chemicals affect river sediment and river water or how long they persist because they are difficult to monitor. To assess undetectable dyes and byproducts in river sediments, we evaluated the potential of river sediment bacteria to degrade dyes and aromatic amines. We describe the natural remediation of river sediment long-contaminated by textile dyeing effluent. After cessation of wastewater discharge, the dye-degradation potential decreased, and the aromatic amine–degradation potential increased initially and then declined over time. The changes in degradation potential were consistent with changes in the sediment bacterial community. The transition occurred on the order of years. Our data strongly suggest that dyes remained in the river sediment and that aromatic amines were produced even in transparent- and no longer colored–river water, but these chemicals were degraded by the changing sediment bacteria. Time-course monitoring of the degradation activities of key bacteria thus enables assessment of the fate of dye pollutants in river sediments. [Display omitted] •Textile dye–polluted river sediment was remediated by bacterial community changes.•Undetectable dyes and byproducts were assessed by monitoring the bacterial activity.•Aromatic amines produced during dye degradation remain in river sediments for years.•Sediment bacterial community degrades the dyes first and then the aromatic amines.