Effect Of Endocrine Disrupting Chemicals Octylphenol And Triclosan On Volatile Fatty Acids From Anaerobic Fermentation

The rapid development of wastewater treatment plants(WWTPs)has resulted in the generation of large amounts of waste activated sludge(WAS).On the one hand,various toxic and hazardous residues in WAS may cause serious environmental problems,which requires proper disposal of WAS.On the other hand,WAS is rich in organic matter and therefore has the potential to generate bioenergy.Therefore,achieving a circular economy through the wasteresource supply chain should be a sustainable method to alleviate the pressure of WAS disposal and achieve bioenergy recovery such as volatile fatty acids(VFAs).However,anaerobic fermentation contains a series of complex biochemical processes,in which several microorganisms and enzymes involved.Because of the sensibility of these microorganisms and enzymes to the environment,the production of VFAs is uncertain.Recently,endocrine disrupting chemicals(EDCs)are frequently detected in wastewater treatment plants,causing widespread concern.It is unclear,however,whether the potential impact of EDCs make contributions to VFA production during anaerobic fermentation.In this study,the VFAproduced anaerobic fermentative system was constructed under the presence of octylphenol(OP)and triclosan(TCS)at different doses(0,20,50,100,and 200 mg/kg TSS).The effects of OP and TCS on the VFA production from fermentation of WAS were investigated by detecting the changes in VFA concentration in reactors with the presence of OP and TCS.Further,the mechanisms of the effects of OP and TCS on VFA production in anaerobic fermentation were studied.The results show that OP has a positive effect on the accumulation of VFAs in anaerobic fermentation,especially acetic acids.As the OP doses increased from 0 to 200 mg/kg TSS,the production of VFAs increased from 3245 to 6828 mg COD/L.Notably,the increase in acetic acid(4425-1511=2914 mg COD/L)accounted for 81.3% of the total increase in VFAs(6828-3245=3583 mg COD/L).Further research found that OP enhanced sludge dissolution and hydrolysis by promoting the biodegradability of WAS,and suppressed the methanogenesis stage by inhibiting the activity of coenzyme F420,resulting the significantly increase in acetic acids.Similar to OP,TCS can also promote the VFA production in anaerobic fermentation of WAS,mainly acetic acids.In the fermentative system with the presence of 200 mg/kg TSS of TCS,the accumulation of VFAs(15083 mg COD/L)was nearly 2-fold that of the control.The percentage of acetic acid in the total VFAs in TCS-contained reactor(200 mg/kg TSS)rose to 74.8%,higher than the 55.1% in the control.Different to OP,however,the presence of TCS could promote all the stages involved in anaerobic fermentation.Noteworthily,the positive effect of TCS on the VFA-producing stage is stronger than that on the VFA-consuming stage(methanogenesis),leading to VFA accumulation.The findings in this study have important reference significance for the in-depth study of the environmental behavior of EDCs in WWTPs and the selection of target products of anaerobic fermentation of EDC-containing WAS.