Treatment of fresh leachate by microaeration pretreatment combined with IC-AO2 process: Performance and mechanistic insight

Abstract

Fresh leachate is commonly featured with high concentrations of degradable organic matters, which can impede the performance of traditional biological treatment, especially the anaerobic reactor. Aiming at improving the biological treatment process of fresh leachate, this study creatively proposed a microaerobic-IC-AO2 (MAICAO2) process and compared it with traditional biological process, then optimized the operating conditions. Meanwhile, this work investigated the transformation rules and molecular compositions of dissolved organic matters (DOM) during MAICAO2 process, particularly the hazardous DOM (antibiotics). The innovative MAICAO2 process can effectively remove 99% chemical oxygen demand (COD), 91% total nitrogen (TN) and 91% ammonia (NH4+-N) during the operation time, and the removal efficiencies of COD, TN and NH4+-N in MAICAO2 process increased approximately 2%, 14% and 13% compared to ICAOAO process. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) confirmed that microaeration could ensure over 53% small molecular organic acids degrade before the subsequent anaerobic reaction so the system could resist the high concentration organic matters stress and improve the denitrification efficiency. Further analysis showed that different categories of antibiotics (including 6 sulfonamides, 4 tetracyclines, 2 macrolides, 4 quinolones and 2 chloramphenicols) could be effectively removed by MAICAO2 process with the total removal efficiency of 50%. This work proposed a new scenario for fresh leachate treatment by proposing the importance of the microaeration pretreatment during the biological treatment process.