Microalgae in aquaculture wastewater: a new forecasting method of production in a marine system
- Autores: Valeria Andreotti
- Directores de la Tesis: Joan García Serrano (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Joan Oca Baradad (presid.), Gianluigi Buttiglieri (secret.), Marco Secci (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencias del Mar por la Universidad de Barcelona y la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
In the field of aquaculture, the main microalgae application is animal nutrition, in which they can be used as an unprocessed component, or as dried material for feed preparations. Moreover, microalgae can assimilate the main nutrients dissolved in aquaculture wastewater reducing the environmental impact of aquaculture and at the same time producing valuable biomass.
Because of the variability of wastewater, it is not easy to predict the microalgae production, nevertheless, the mathematical model could offer the possibility to study microalgae growth in different conditions.
Mathematical models are used to forecast algal productivity and nutrient removal efficiency in synthetic media and in urban wastewater, but they were never been implemented and calibrated for aquaculture wastewater.
The main outcome of the present Ph.D. thesis was to calibrate and validate the integrated mechanistic model BIO_ALGAE with experimental data obtained from the cultivation of marine microalgae in aquaculture wastewater. This model includes crucial physical and biokinetic processes to simulate microalgae growth in wastewater, and in a different type of photobioreactors. BIO_ALGAE was used to understanding the slight diurnal variations, which could have not been detected with experimental samples.
Preliminary respirometric tests were carried out on the microalgal-bacterial suspension. These respirometric outputs were compared with process rates affecting dissolved oxygen dynamics computed by the mathematical model.
In the experimental part of this thesis project, the productivity and capacity in the bioremediation of three marine microalgae species, Tetraselmis suecica, Dunaliella tertiolecta and Isochrysis galbana was investigated and compared. Wastewater generated during the production of grey mullet (Mugil cephalus) and sea bream (Sparus aurata) was used as culture medium.
The experiments were conducted in batch and in semi-continuous conditions using column photobioreactors with differents volumes.
It is known that under different stress conditions, the microalgae produce bioactive compounds, therefore, aquaculture wastewater was used as substitute synthetic cultivation medium to test the production of lipids, proteins, and carbohydrates in the microalgal biomass. Moreover, these species were cultivated in unsterilized culture media, and this reduces energy consumption, costs, and efforts.
This study confirms the potential to employ Tetraselmis suecica in an Integrated Multi-Trophic Aquaculture system for biomass production and bioremediation of wastewater and identifies Dunaliella tertiolecta as another valid candidate species.
T. suecica was therefore selected for the validation of BIO_ALGAE model.
For the first time, BIO_ALGAE model was applied in aquaculture system and highlights a good agreement between experimental data and simulations.
This model has proved to be an efficient tool to understand microalgae production in aquaculture wastewater treatment and to simulate the dynamics of different conditions in closed photobioreactors. Indeed, BIO_ALGAE describes the factors that influence microalgae growth and this is a useful approach to predict microalgal biomass with the optimization of the operating conditions.
