Enhanced Tetracycline Removal through Integrated Adsorption, Biodegradation, and Chemical Degradation in H2O2 Assisted VFAs-Producing Anaerobic Digestion

The presence of tetracycline in wastewater poses challenges for anaerobic digestion (AD) systems due to its recalcitrant nature leading to accumulation in sewage sludge and potential inhibition of microbial activity. Herein, tetracycline removal and its impacts on carbon-flow performance and microbial stability were investigated in anaerobic sludge systems targeting methane production (AD biogas ) or volatile fatty acid accumulation (AD VFAs ). The results showed that tetracycline significantly impaired methanogenic carbon conversion in AD biogas , decreasing CH 4 production from 400.46 ± 48.96 to 294.67 ± 64.48 mL g -1 [VS] accompanied by severe cellular damage. In contrast, VFAs accumulation in AD VFAs showed minimal change under 10 mg L -1 tetracycline exposure (12,352 ± 1,421 vs 13,009.11 ± 956.19 mg COD L -1 ). The stable malondialdehyde level despite increased soluble exopolysaccharide production suggests soluble exopolysaccharide mitigated tetracycline-induced oxidative stress. At an initial tetracycline concentration of 10 mg L -1 , the AD VFAs system achieved a significantly higher tetracycline degradation efficiency (92.38 ± 0.32%) than the AD biogas system (50.88 ± 2.07%). Although biodegradation occurred in both systems, the superior performance of AD VFAs was primarily attributed to H 2 O 2 /Light assisted oxidative degradation involving hydroxyl radicals. These results have demonstrated that integrated H 2 O 2 /Light can be an effective approach to achieve both VFAs production and removal of recalcitrant contaminants.