GRanular microalgae-bacterial sludge for Aquaculture wastewater Treatment

Marine aquaculture may negatively affect the coastal environment if not properly monitored and operated. Aquaculture activities significantly impact the ecosystems, being the high use of water and wastewater discharge the major drawbacks for its environmental sustainability. The recirculating aquaculture systems (RAS) are extremely important as they allow water recycling/reuse. In this way, aquaculture farms can save water which in turn represent resource and economic savings for the aquaculture industries. To achieve an adequate production, fish farms use significant amounts of antibiotics as therapeutic, growth-promoting and prophylactic measures. The discharge of these micropollutants into the coastal water bodies represent not only a source of contamination but also can favor the emergence of antibiotic resistance genes. Therefore, new technologies able to properly treat aquaculture wastewater to ensure water quality appropriate for the its reuse are needed.
Biofilm systems are particularly promising for the treatment of wastewater, especially those containing micropollutants such pharmaceuticals. The high microbial biomass and the layered structure of biofilms offers protection to the microbial community against the adverse conditions present in the wastewater. Although belonging to different trophic levels, both microalgae and bacteria have demonstrated ability to deal with recalcitrant wastewaters. The combination of microalgae and bacteria within the same structure could be beneficial for the treatment of wastewater as the synergy established between them could turn the process more efficient.

The present project aims to develop algal-bacterial granular sludge that will be further used in bioreactor system aiming at treating wastewater from marine aquaculture systems. Microalgae strains isolated from different marine environments will be used in combination with activated sludge to produce mixed microbial granules. The feasibility of the developed aggregates to treat marine aquaculture wastewater in SBR systems will be assessed. As the developed technology aims to produce water to be reused in the aquaculture facilities, the microbiological safety and quality of the recycled water should be ensured and will be assessed. Moreover, to better understand the evolution and dynamics of the populations inhabiting the granular sludge, the microbial community will be studied using molecular biology techniques Collectively, the outcome of this project will not only advance the field of wastewater treatment, but it will also benefit the aquaculture farms and ultimately the society by reducing the energy consumed during wastewater treatment and the water use as this resource can be reused in the facilities