The effect of Np-magnetite on the granulation process of an SBR reactor used for domestic wastewater treatment
2021
Domingos, Dayane Gonzaga | Libardi, Nelson | Henriques, Rosana Oliveira | Xavier, Jéssica Antunes | da Costa, Rejane Helena Ribeiro
This study investigated the effect of magnetite nanoparticles (Np-magnetite) added to a pilot-scale sequencing batch reactor (SBR) treating domestic wastewater, to improve aerobic granular sludge (AGS) formation and the effects of granule disintegration. Np-magnetite additions (75 mg L⁻¹) were made during the start-up of the reactor and repeated after 100 and 170 days, when granule disintegration was observed. From the first Np-magnetite addition, SVI₅ was reduced from 1315 to 85 mL g⁻¹. The granular biomass was observed on the 56th day, when 57% of the granules presented diameters bigger than 212 µm. The 100-day disintegration episode disturbed the granular biomass, reducing the volatile suspended solids by 51%, increasing the SVI values to above 200 mL g⁻¹. Np-magnetite addition recovered all the granular biomass parameters to the values observed before disintegration. The treatment efficiency was stable during operation of the reactor for nutrients (52.8 ± 23.4% NH₄⁺–N; 54.5 ± 12.2% PO₄³⁻–P) and carbonaceous organic matter (71.7 ± 12.7% BOD₅; 77.5 ± 10.0% CODₜ). Np-magnetite addition changed the microbial community of the granular sludge, analysed via high-throughput 16S RNA sequencing, and recovered the treatment efficiency previously disturbed by the disintegration processes. These results indicate the potential of Np-magnetite as an agent for sludge aggregation in an aerobic granular reactor.
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