| In recent years,with the acceleration of the urbanization process,the amount and scale of urban sewage treatment in my country have increased rapidly.Waste activated sludge(WAS)is an extremely complex by-product in Wastewater treatment plants(WWTPs).On the one hand,WAS has the characteristics of large output,easy corruption,pathogenic microorganisms and heavy metals.If it is not properly disposed of,it will cause secondary pollution to the environment.On the one hand,the WAS is rich in organic matter such as a large amount of protein and carbohydrates,and is considered to be a renewable bio-energy.As an efficient pollution control and energy recovery technology,Anaerobic digestion of WAS has received extensive attention and application in the environmental field.However,the presence of toxic pollutants such as polycyclic aromatic hydrocarbons(PAHs)in the WAS may interfere with this process.In this paper,the effects of anthracene(ANT)and naphthalene(NAP)on methane production from anaerobic digestion of WAS were systematically investigated.The anaerobic digestion of WAS by ANT and NAP was investigated through the processes of solubilization,hydrolysis,acidogenesis,and methanogenesis processes,the physical and chemical properties of WAS,the interaction of PAHs with proteins and polysaccharides,and the changes of key enzymes and microbial community structures.The results showed that when the ANT concentration was increased from 0 mg/kg TSS to 200 mg/kg TSS,the maximum cumulative methane yield decreased from 122.42 mL/g VSS to 107.12 mL/g VSS.Gompertz model analysis showed that the methane yield potential of WAS was negatively correlated with the content of ANT.At the same time,the presence of ANT in WAS not only inhibits intermediate biochemical processes such as solubilization,hydrolysis,acidogenesis,and methanogenesis processes,(the degree of inhibition is:methanogenesis>acidogenesis>hydrolysis),but also interacts with proteins and reduces the bioavailability of matrix.Further studies showed that ANT not only inhibited the activity of the key methanogenesis enzyme coenzyme F420,but also reduced the number of bacteria and archaea in the anaerobic digestion system and changed the microbial community structure,reducing the abundance of methanogenic archaea such as Methanobacterium and Candidatus_Methanofastidiosum.The presence of NAP also inhibited the methane production from anaerobic digestion of WAS.When the concentration of NAP increased from 0 mg/kg TSS to 100 mg/kg TSS,the maximum methane yield potential decreased from 149.43 mL/g VSS to 133.80 mL/g VSS.Due to the lipophilic properties of naphthalene,the particle size of sludge flocs is increased,which hinders the release of organic matter in the WAS into the liquid phase,resulting in the inhibition of the dissolution of soluble proteins and carbohydrates.NAP has effect on the main intermediate biochemical processes of anaerobic digestion.It has a certain inhibitory effect,the hydrolysis process is seriously inhibited,and the inhibition of protein degradation rate is higher than that of polysaccharides.The reason is that NAP has a greater impact on protein functional groups by Fourier transform infrared spectroscopy(FTIR).The activities of key enzymes(such as protease,α-glucosidase,AK and coenzyme F420)in anaerobic digestion of WAS all have a certain inhibitory effect,and the inhibitory effect increases with the increase of NAP concentration.And NAP reduced the number of bacteria and archaea in the anaerobic digestion system and changed the microbial community structure,reducing the abundance of methanogenic archaea such as Methanosaeta and Methanobacterium.In this paper,the effects and mechanism of ANT and NAP on methane production from anaerobic digestion of WAS were revealed,which provided an important reference and theoretical basis for the recycling and stabilization of WAS containing PAHs. |
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