The Effect Of Different Straws On Anaerobic Removal Of Ficiency And Mechanism Of Polycyclic Aromatic Hydrocarbons In Sludge By Co-metabolism Pathway

Anaerobic digestion?AD?technology not only processes a range of solid waste,but also produces clean energy biogas.However,there are many shortcomings in the single anaerobic digestion of sludge,such as low biogas production and low removal efficiency of toxic organic pollutants in sludge.How to further reduce the content of typical toxic organic pollutants in sludge has attracted much attention,such asPolycyclic Aromatic Hydrocarbons?PAHs?.In this study,corn,wheat and rice straw were used as co-matrix and were added into the sludge according to different organic matter contents?volatile solids?VS?mass ratio?of 1:0.5,1:1 and 1:1.5.The sludge is subjected to anaerobic co-metabolism.The effects of different types of straw on biogas production,biogas composition,microbial diversity,PAHs removal efficiency during sludge anaerobic digestion and the mechanism of straw-promoting PAHs degradation were investigated.Anaerobic digestion of sludge without added straw was used as a control group?CK?.The results show as follows:?1?The addition of straw can significantly increase the daily biogas production and methane component,and the daily biogas production increases with the increase of straw addition.Among them,when the ratio of sludge to corn stover is 1:1.5,it has a strong promoting effect on the daily yield of biogas and methane component,which can reach 2303.08 mL·d^-1 and 52.48%.?2?Compared with the CK group,the addition of straw can promote the degradation of?PAHs in the sludge.Among them,when the ratio of sludge to rice straw is 1:0.5,it has a strong effect on the degradation of PAHs,and the average degradation rate can reach 51.33%.At the same time,the addition of straw also has a strong promoting effect on the degradation of 4-ring aromatic benzo?b?fluoranthene?BbF?and benzo?k?fluoranthene?BkF?.Among them,the addition of rice straw is more conducive to the degradation of BbF and BkF,the average degradation rate can reach up to 69.93%(VS _sludge:VS _rice=1:1.5)and 68.76%(VS _sludge:VS _rice=1:0.5).?3?After the addition of straw,each experimental group was classified into Chloroflexi,Proteobacteria,Bacteroidetes,Firmicutes,Aminicenates,Cloacimonetes?bacteria?and Euryarchaeota and Bathyarchaeota are dominant microbial at phylum level.Among them,the relative abundance of Bacteroidetes,Cloacimonetes and Bathyarchaeota increased with the addition of straw.At the class level,the addition of straw promoted the growth of Synergistia,Anaerolineae and Bacterodidia_vadinHA17.At the genus level,the addition of straw promoted the growth of Christensenellaceae_R-7_group,unclassified_fRuminococcaceae,unclassified_pCloacimonetes,Bacteroides?bacteria?and Methanomassicicoccus?archaea?.?4?The addition of straw can promote the degradation of PAHs in the sludge by increasing the dehydrogenase activity in the system and the relative abundance of some microorganisms.With the addition of straw,the relative abundance of microorganisms with degradable organic compounds in the system will increase,such as Bacteroidetes,Verrucomicrobia?bacteria?and Bathyarchaeota?archaea??phylum level?;Bacteroidia,Bacterodidia_vadinHA17,Anaerolineaceae,Synergistetes?bacteria??classlevel?;norank_cBacteroidetes_vadinHA17,norank_fAnaerolineaceae?bacteria?and norank_pBathyarchaeota?archaea??genus level?.Among them,Verrucomicrobia,Bathyarchaeota,Anaerolineaceae,norank_fAnaerolineaceae and norank_pBathyarchaeota also have a certain promoting effect on the degradation of hydrocarbon compounds.Moreover,the addition of rice straw is more conducive to the growth of the above-mentioned flora,thereby further promoting the degradation of PAHs in the sludge.