Effect Of Triclosan On Anaerobic Fermentation From Waste Activated Sludge And Its Regulation

Triclosan(TCS),a typical broad-spectrum antibacterial agent,is extensively added to various products such as nursing products,medical supplies,and household cleaning products.More than 50%of TCS would be transferred from wastewater to waste activated sludge(WAS)in wastewater treatment processes,resulting in its significant accumulations in WAS.Owing to the growing use of TCS-based products,TCS content in WAS may further increase in the future.Thus,the interaction between TCS and WAS treatment necessitates to be evaluated urgently.However,the interaction between TCS and WAS anaerobic fermentation was rarely reported.This work therefore aimed to fill the gap through deeply understanding the degradation pathway of TCS in WAS anaerobic fermentation and its impact on anaerobic fermentation.To obtain comprehensive information,we first investigated the degradation and transformation of TCS in anaerobic sludge system using batch and long-term tests.Experimental results showed that～4 5%of TCS was respectively degraded in long-term(65 d)anaerobic fermentation.Based on the information from HPLC-MS analysis,the degradation products of TCS were determined(2,4-dichlorophenol as its main intermediate)and three pathways i.e.,dichlorination,hydroxylation and cleavage of ether bonds,were proposed for TCS degradation.Then,the effect of TCS at different dosages(12-487 mg/kg TSS)on hydrogen production were explored using real sludge as the fermentation substrate.With an increase of TCS from 12 to 487 mg/kg TSS,the maximum hydrogen yield decreased from 18.6 to 12.8 mL/g VSS.Details of how TCS and its main metabolism products affected anaerobic fermentation were explored through assessing the processes of sludge solubilization,hydrolysis,acidogenesis and acetogenesis,using either real sludge or synthetic wastewater as fermentation substrates.It was found that the main reason for this inhibition was TCS significantly suppressed acidogenesis.The effect of TCS on microbial characteristics of the anaerobic fermenter was clarified through the analysis of community composition.TCS enhanced the relative abundances of complex organic degradation microbes such as Guggeheimella and Conexibacter but decreased the relative populations of hydrogen producers such as Proteiniborus and Corynebacterium.Finally,potassium ferrate(PF)was used to mitigate the toxicity of TCS to WAS anaerobic fermentation.With an increase of PF from 0 to 0.09 g/g,the maximum hydrogen yield increased from 11.4 to 14.5 mL/g VSS.It was found that PF enhanced the disintegration of sludge cells and increased the maximum hydrogen accumulation.