Closed-loop operation of a simulated recirculating aquaculture system with an integrated application of nonlinear model predictive control and moving horizon estimation

•A new closed-loop framework for recirculating aquaculture systems is presented.•Nonlinear Model Predictive Control and Moving Horizon Estimation are considered.•Proposed approach showed potentials in controlling the rearing environment.•Water quality parameters remained within limits while using the closed-loop framework.•Proposed framework can maintain the system on target under multiple scenarios. High water recirculation combined with a low rate of water exchange can deteriorate water quality and affect fish welfare in recirculating aquaculture systems (RAS). A nonlinear model predictive controller (NMPC) integrated with moving horizon estimation (MHE) was implemented in this work to maintain water quality parameters (e.g., oxygen, ammonia, and nitrate concentration) in RAS. The performance of the proposed control scheme was then evaluated in the presence of process uncertainty and measurement noise with full and partial accessibility to the system’s states under several common scenarios that can arise during the operation of RAS. In all scenarios, the proposed framework showed acceptable performance in keeping the water quality parameters close to their setpoints, demonstrating the high potential of this strategy in closed-loop operation of RAS.