Next-generation continuous-flow SBR technology for municipal wastewater treatment: Design and optimisation

Continuous-flow Sequencing Batch Reactors (SBR) are a promising technology for biological wastewater treatment due to the lower footprint and energy consumption compared to continuous reactors and variable-volume SBRs. To maximise the benefits of this technology, a proper understanding and optimisation is crucial. Thus, this study developed a design procedure for continuous-flow SBR and assessed reactor performance for municipal wastewater treatment. A design procedure was developed for reactor dimensioning as a function of kinetics, wastewater composition and imposed SRT. Specific design features were included to account for the SBR operation: the applied organic loading rate, and the definition of the anoxic-aerobic fractions and duration. This procedure was proven suitable to design a continuous-flow SBR and could be applied to other SBR technologies. Reactor operation was assessed by developing a dedicated model to analyse the behaviour of a full-scale, continuous-flow SBR with reverse flow operation, branded as LUCAS®. For this purpose, carbon and nitrogen removal performance was evaluated under different aeration strategies. Strong cycle dynamics were observed as a consequence of the reactor hydraulics, biokinetics and operational cycle distribution. Nevertheless, the COD and nitrogen removal efficiencies were 85 % and 67-90 %, respectively. Also, higher nitrogen removal efficiency was observed with lower aerobic-anoxic ratios. Overall, the effluent requirements were fulfilled in all the scenarios. Additionally, potential extensions of the given reactor configuration were explored, including the feasibility of biological phosphorus removal or reactor performance with aerobic granular sludge. The current reactor configuration showed potential for biological phosphorus removal, but the cycle distribution requires further improvements to achieve high removal efficiencies. The presence of aerobic granular sludge improved nitrogen removal up to 94 %. Overall, the results of the dedicated model set up in this study provided a good process understanding and will help to promote the application of this technology under optimal conditions.