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ABSTRACT
The discharge of untreated textile dyeing wastewater containing azo dyes has significant ecological consequences. The incomplete biodegradation of these dyes can produce harmful and carcinogenic aromatic amines (AAs), which pose a threat to the environment. This study evaluates the treatment of real textile dyeing wastewater containing azo dyes by two different systems: an anoxic sequential batch reactor (A/O-SBR) and an aerobic sequential batch reactor (A-SBR). The effects of hydraulic retention time (HRT) on both systems were investigated in terms of chemical oxygen demand (COD), total nitrogen (TN), color, and AAs removal. Ranging between 85% and 92%, the COD removal efficiency was almost similar in the A/O-SBR and A-SBR systems, suggesting that the aerobic phase is primarily responsible for COD removal. However, A/O-SBR showed higher removal of color (90%) than A-SBR (75%) due to the presence of an anoxic phase. HRT has a significant impact on color removal in both systems. However, there was no significant effect on COD removal when HRT exceeded 12 h. According to LC-MS/MS analysis, increasing the HRT from 12 h to 24 h increased the AAs concentration in the anoxic phase, from 253 ng/L to 261 ng/L and slightly decreased the AAs concentration in the aerobic phase from 107 ng/L to 102 ng/L. This resulted in an overall improvement in both dye and AAs removal. The presence of aerobic phase in A/O-SBR and A-SBR demonstrates strong AAs removal capacity. GC-MS/MS analysis indicated that as the HRT of A/O-SBR and A-SBR increased, the number of by-products increased.
Acknowledgements
The authors express their gratitude to Mr. Varol Çetinkaya from Füzyon Water Technologies and Automation Industry Trade Co. Ltd. for generously providing the pilot-scale system of the A/O-SBR and A-SBR. This valuable contribution greatly facilitated the experimental setup and allowed for the successful implementation of the study.
Disclosure statement
No potential conflict of interest was reported by the author.
Supplementary data
Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2023.2241402
Additional information
Notes on contributors
Ahmed Albahnasawi
Dr. Ahmed Albahnasawi is a research fellow in the Environmental Engineering Department, at Gebze Technical University, Turkey. Albahnasawi's research interests include the application and design of microbial fuel cells integrated with Fenton oxidation for industrial wastewater treatment/solid waste management and monitoring of organic micropollutants by both chromatographic and spectrophotometric analyses.