Effect Of Diclofenac On The Production Of Volatile Fatty Acids From Anaerobic Fermentation Of Waste Activated Sludge And Its Relevant Mechanisms

Activated sludge process is a commonly used treatment process in wastewater treatment plants(WWTPs).The process has the advantages of good biological treatment efficiency and low operating cost.However,the process could produce substantial waste activated sludge(WAS),which contains high levels of pathogens,heavy metals and other toxic and hazardous substances.If the sludge is not effectively disposed,it will cause secondary pollution to the environment.On the other hand,WAS contains a lot of organic matter such as protein and carbohydrates,and therefore it is a valuable resource available.Anaerobic fermentation technology has been considered a recommended method for sludge treatment.By sludge anaerobic fermentation,the organic matter in the sludge can be bio-converted into energy substances such as hydrogen,methane,volatile fatty acids(VFAs)and so on.Recently,the production of VFAs from sludge anaerobic fermentation has attracted scholars' attention because the production of VFAs can be used as the preferred carbon source for biological nitrogen and phosphorus removal.To date,the studies on the production of VFAs from sludge anaerobic fermentation have mainly focused on the pretreatment methods and the optimization of operation parameters.Sludge contains not only biodegradable proteins,carbohydrates,polyhydroxyalkanoate,but also a variety of pollutants such as heavy metals and pharmaceuticals and personal care products(PPCPs).Diclofenac(DCF)as a PPCP can play an anti-inflammatory analgesic effect by mainly inhibiting prostaglandin synthesis.It is reported that the annual consumption of DCF around the world can be up to 940 t,and this consumption will continue to increase in the future with the increase of population and the rapid development of economy.As the last barriers before DCF entering into the natural environment,WWTPs can reduce the DCF content via enrichment,adsorption,degradation,etc.The concentrations of PPCPs in the environment are usually at PPB(ng/L)level,but DCF has been detected to reach PPM(?g/L)level.Although useful information of the DCF's biological toxicityis available,the little imformation of the potential impact of DCF on sludge anaerobic fermentation can be found,and the mechanism of DCF on sludge anaerobic fermentation is not clear so far.Therefore,the main aim of this work is to assess the potential impact of DCF onsludge anaerobic fermentation.Firstly,the productions of VFAs from sludge with different dosages of DCF were compared.Secondly,the impacts of DCF on each process involved in sludge fermentation were investigated.Finally,the activities of key enzymes responsible for VFAs production and microbial community were also analyzed.The findings achieved fill the gap between sludge anaerobic fermentation and the emerging contaminant,DCF,and may have important implications to sludge treatment in the future.