IMTA-RAS Systems -- Modeling, Control, and Design of Experiments

An Integrated Multi-trophic Aquaculture (IMTA) system contains multiple aquatic species from different trophic levels, farmed in an integrated manner to improve efficiency, reduce waste, and provide ecosystem services such as bioremediation. A Recirculation Aquaculture System (RAS) recycles fish tank water, thereby reducing operating costs and disease risks. In RAS, fish tank wastewater is typically treated by bacterial biofilters, oxygenated, and recirculated.

Combining IMTA and RAS into an IMTA-RAS system aims to optimize nutrient utilization by recycling aquaculture waste as food for co-cultured species. The integration of RAS and IMTA also supports the development of new aquaculture products, potentially increasing economic returns.

Example of hydrodynamic simulation in an IMTA-RAS tank: CFD modelling allows to analyse the flow and light conditions important for algae growth.

Beyond biological aspects, successful IMTA-RAS operation requires proper design and management of all system components, including sensors and control algorithms. A specific area in the research and development of algae cultivation systems is the modeling and simulation of hydrodynamic conditions using computational fluid dynamics (CFD). CFD simulations are used to determine the light regime algae are exposed to [1], or to predict algae growth by integrating fluid dynamics and reaction kinetics [2]. For the experimental design problem in model identification, see our works [3, 4, 5].

Experimental laboratory tank with bottom aeration for Ulva ohnoi cultivation. The arrows determine the velocity of the macroalgae fronds.

This project highlights both the complex interactions of biotic and abiotic factors influencing the performance and stability of IMTA-RAS systems and the current lack of reliable mathematical models and empirical data for optimizing the growth of macro- and microalgal consortia in IMTA-RAS tanks. As a solution, we propose a comprehensive mechanistic approach to modeling and optimizing consortium growth within IMTA-RAS.

The project includes:

1. Design of experimental devices with relevant sensors and state observers for small-scale and laboratory cultivations;
2. Mathematical modeling of light distribution and multiphase fluid dynamics within aerated tanks using a suitable CFD code;
3. Design of experiments for further IMTA-RAS modeling and optimization of operational conditions for cultivation of algae consortium.