Effect of cephalexin after heterogeneous Fenton-like pretreatment on the performance of anaerobic granular sludge and activated sludge

Effects of Fe3O4 NPs heterogeneous Fenton-like pretreatment on the physicochemical properties and microbial community structure of anaerobic granular sludge (AGS) and activated sludge (AS) with cephalexin were investigated. Results showed that the average removal rate of chemical oxygen demand (COD) by the AGS was 80.9%, 85.9%, 90.3% and 91.6%, respectively, at cephalexin without pretreatment, pretreatment with 20% (H2O2), 40% (H2O2) and 60% (H2O2). Compared to the reactor without pretreatment, the COD removal rate increased by 24.14% with 60% (H2O2) pretreatment for the AS. Dehydrogenase levels in the AS were 313.05, 351.12, 434.81 and 480.77 mg TF (g.h)(-1), which increased with higher concentrations of the pretreatment. Three-dimensional fluorescence (EEM) spectra analysis showed that the absorption peak intensities of humic acid in soluble microbial products (SMP) decreased in the AGS with increasing pretreatment. In the AGS, the dominant bacterial populations were Levilinea, Litorilinea and Clostridium sensu stricto. Clostridium sensu stricto accounting for 4.35% without pretreatment, while it was as high as 17% when it was pretreated with 60% (H2O2). The increase in the proportion of Clostridium sensu stricto was beneficial to the removal of organic pollutants. The pretreatment was also beneficial to the growth of acetic acid producing Methanothrix. For the AS, Gemmobacter were the dominant species, which increased from 6.56% to 32.61% after increasing the pretreatment to 40% (H2O2). Furthermore, the microbial capacities of amino acid metabolism and carbohydrate metabolism were enhanced by addition of pretreatment. (C) 2019 Elsevier Ltd. All rights reserved.