Performance of an anaerobic co-digestion system treating commercial remazol blue rsp dye and real honey wastewater: decolorization, stability, and detoxification

Background: This study aimed to evaluate the performance of an anaerobic co-digestion (AcoD) system in dye detoxification, decolorization, and chemical oxygen demand (COD) removal. Methods: Herein, synthetic textile (Remazol blue RSP) wastewater (50, 100, and 150 mg/L) and real honey wastewater were anaerobically co-digested using an anaerobic up-flow reactor at a hydraulic retention time (HRT) of 24 h and a C:N ratio of 5:1. Total alkalinity (TA) and volatile fatty acid (VFA) were measured using spectrophotometric method, while color removal was monitored at λ max 595 nm. COD removal was measured using the closed reflux titrimetric method. The phytotoxicity test was conducted based on germination percentage, relative toxicity, and Phaseolus vulgaris plumule length. Results: COD removal at 50, 100, and 150 mg/L dye concentrations was relatively similar, as 76.69±1.33%, 75.91±2.1%, and 75.77±2.83%, respectively. The decolorization rate decreased with the increase in dye concentration from 97.37±2.18% to 92.22±0.51% and 90.12±0.49%. VFA/(TA) ratio markedly increased with increasing dye concentration, from 0.05 to 0.32 and 0.35, indicating system instability. Additionally, the phytotoxicity test revealed that the AcoD system improved the effluent quality and reduced dye wastewater toxicity. Conclusion: The findings suggest that AcoD of textile and honey wastewater can effectively remove pollutants (COD), detoxify, and decolorize Remazol Blue RSP-containing synthetic wastewater. Upon increasing dye concentration, a decrease in decolorization rate and system instability were observed, reflecting the effect of dye toxicity on the anaerobic system.