Preparation And Modification Of Antibiotic Residue Biochar And Its Enhanced Anaerobic Digestion Performance

Anaerobic digestion is considered as a sustainable technology to stabilize and reduce organic waste and is widely used in wastewater and solid waste treatment.However,there are some technical challenges with anaerobic digestion,such as low gas production during digestion,low methane content and digestive system instability.Biochar has been proved to enhance the gas production performance of the digestive system by regulating the buffer capacity of the system and improving microbial activity.Therefore,how to improve the ability of biochar to enhance anaerobic digestion is a problem worthy of study.Based on biochar enhanced anaerobic digestion technology,the preparation of phosphoric acid modified and loaded nano zero valent iron biochar was carried out.The effect of biochar addition on anaerobic digestion performance was studied in sequential batch and semi-continuous state.The experimental conclusions are as follows:1)Primordia biochar,phosphoric acid modified biochar PBC（H₃PO₄-modified biochar）and zero-valent iron nanoparticle（nZVI）biochar（nZVI/PBC）supported by PBC were prepared from streptomycin residue at six temperatures（250,350,450,550,650 and750°C）.The results showed that the optimum temperature for biochar preparation from streptomycin residue pyrolysis was 550°C.After phosphoric acid modification,obvious pore structure appeared on the surface of biochar,and its carbon content and specific surface area increased to 43.03%and 337.347 m²·g^-1.The EDC of BC550,PBC and nZVI/PBC were 0.006±0.002,0.12±0.005 and 0.16±0.004 meq·g^-1.The agglomeration of nZVI particles was reduced and the electron-giving ability of biochar was enhanced by using PBC as the carrier to load nZVI.2)The comparison of PBC and nZVI/PBC in enhancing the performance of digestive system showed that both biochar could improve the performance of digestive system gas production,and biogas production increased by 29.63%and 29.26%,respectively.But compared with PBC,nZVI/PBC showed higher ability in maintaining digestive system stability and promoting fiber degradation.At the same time,after adding biochar,a large number of microorganisms attached to the surface of biochar,and the microbial diversity was significantly improved.Chloroflexi,Actinobacteriota and Methanosaeta at phylum level were enriched.However,the addition of nZVI/PBC had a better enrichment effect on microorganisms.3)The experimental results showed that adding nZVI/PBC on the performance of anaerobic digestion system in semi-continuous state can basically maintain the p H value of the experimental group around 7.2.Under the three organic loading conditions,the daily methane production of nZVI/PBC group was 53.5,92.0 and 176.6 m L,which increased by 14.71%,14.81%and 18.36%compared with CK group,and methane content was 57.56%,65.45%and 67.25%,respectively.Compared with CK group,the VS removal rates were 43.54%,39.13%and 45.62%,and the VS removal rates were 17.91%,12.72% and 23.10%,respectively.