The effect of Np-magnetite on the granulation process of an SBR reactor used for domestic wastewater treatment

Comprehensive analysis of effects of magnetic nanoparticles on aerobic granulation and microbial community composition: From the perspective of acyl-homoserine lactones mediated communication

As dosing additives benefit for aerobic granular sludge (AGS) cultivation, effects of different concentrations (0, 10, 50 and 100 mg/L) of magnetic nanoparticles (Fe3O4 NPs) on aerobic granulation, contaminant removal and potential microbial community evolution related to acyl-homoserine lactones (AHLs) mediated bacterial communication were investigated with municipal wastewater. Results showed that the required time to achieve granulation ratio > 70 % was reduced by 60, 90 and 30 days in phase II with addition of 10, 50, 100 mg/L Fe3O4 NPs, respectively. 50 mg/L Fe3O4 NPs can improve contaminant removal efficiency. The promotion of relative abundance of AHLs-producing and AHLs-producing/quenching populations and AHLs-related functional genes accompanied with faster granulation. Iron-cycling-related bacteria were closely related with AHLs-related bacteria during AGS formation. Co-occurrence network analyses showed that AHLs-mediated communication may play an important role in coordinating microbial community composition and functional bacteria participating in nitrogen and polyphosphate metabolisms during aerobic granulation process.

Enhanced aerobic granular sludge formation by applying Phanerochaete chrysosporium pellets as induced nucleus

The long start-up period is a major challenging issue for the widespread application of aerobic granular sludge (AGS). In this study, a novel rapid start-up strategy was developed by inoculating Phanerochaete chrysosporium (P. chrysosporium) pellets as the induced nucleus in a sequencing batch airlift reactor (SBAR) to enhance activated sludge granulation. The results demonstrated that P. chrysosporium pellets could effectively shorten the aerobic granulation time from 32 to 20 days. The AGS promoted by P. chrysosporium pellets had a larger average diameter (2.60-2.74 mm) than that without P. chrysosporium pellets (1.78-1.88 mm) and had better biomass retention capacity and sedimentation properties; its mixed liquor suspended solids (MLSS) and sludge volume index (SVI₃₀) reached approximately 5.2 g/L and 45 mL/g, respectively. The addition of P. chrysosporium pellets promoted the secretion of extracellular polymeric substances (EPS), especially protein (PN). The removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) in P. chrysosporium pellets reactor were 98.91%, 89.17%, 64.73%, and 94.42%, respectively, which were higher than those in the reactor without P. chrysosporium pellets (88.73%, 82.09%, 55.75%, and 88.92%). High throughput sequencing analysis indicated that several functional genera that were responsible for the formation of aerobic granules and the removal of pollutants, such as Acinetobacter, Pseudomonas, Janthinobacterium, and Enterobacter, were found to be predominant in the mature sludge granules promoted by P. chrysosporium pellets.