Phycoremediation as a circular bioeconomy process: unlocking microalgal potential for biomolecule production and wastewater treatment

Abstract

Wastewater treatment processes have evolved in recent years due to the complexity of this residue generated worldwide. In recent years, there has been an increasing focus on integrating phycoremediation systems as a possible option for treatment processes. This doctoral thesis seeks to integrate and highlight all the benefits and processes involved in an established phycoremediation system and show its potential to be considered as a circular bioeconomy process. This thesis aims to provide guidance on why these systems can be installed in various areas and what their potential benefits might be. From wastewater treatment to biomolecules production, from microbial control to the reuse of water treated by this system, this doctoral thesis seeks to integrate all these processes through the analysis of previous studies and experimental work. In this research, it was evaluating the conditions of availability of nutrients (nitrogen, phosphorus and sulfur) that allow the greatest accumulation of value biomolecules from three strains of microalgae (Chlamydomonas reinhardtii, Chlorella vulgaris, and Scenedesmus sp.), to establish the implications of macronutrient variation in the accumulation of biomolecules and to visualize their possible impact on wastewater treatment. Microalgae can be grown in wastewater, making this a circular process, obtaining a valuable by-product derived from the reuse of this waste. In this way, it was evaluated the growth of one of the microalgae strains in two types of wastewaters. Determining by this way, the possibility to use wastewater as culture medium without affecting the productivity of biomolecules of interest for their next bioconversion. Finally, an evaluation of the behavior of bacteria during wastewater treatment was carried out, to determine if phycoremediation process can reduce these microorganisms and thus reduce the chlorination process in common wastewater treatment. This research in this sense shows the potential of producing microalgae biomolecules using wastewater as a culture medium for their bioconversion into valuable products such as bioplastics and one of the most interesting benefits of using phycoremediation as a method of wastewater treatment: microbial control.