Description of new single-chamber continuous-flow reactors of aerobic granular sludge: Technical and biological study

Abstract

Aerobic granular sludge reactors usually operate in sequential batch mode, although this configuration limits the treatment of large volumes of wastewater, and they require a storage system. To implement this technology at full-scale, it would be necessary to design a simple and compact continuous-flow bioreactor able to treat larger volumes of wastewater. In this study, four aerobic granular sludge single-chamber continuous-flow reactors (R1, R2, R3 and R4) were designed and operated at the lab scale to evaluate and select a bioreactor configuration that achieves high organic matter removal performance while maintaining a stable granulation for long-term operation, promoting the washout of filamentous microorganisms. Results confirmed that the bioreactor including a lateral decanter (R1), was able to work in a steady state without loss of granular biomass and reached 95% of organic matter removal performance. Its granules had excellent compaction, with settling velocity values above 100 m·h−1. The R1 bioreactor also allowed rapid biomass adaptation and therefore a fast start-up (11 days). Results of this preliminary study at the lab scale suggested that the new and simple bioreactor design could be promising for its implementation at full scale. For that, future research is required to optimise the current model and to determine the most suitable operational parameters to treat domestic wastewater at full scale.