Improving nutrient and water use efficiencies in multi-loop aquaponics systems

The sustainable development of agricultural systems where nutrients and water are recycled to a high degree is of enormous importance. Traditional aquaponics, where fish and plants are cultivated in one recirculating system, addresses these ecological challenges, but still struggles with its economical feasibility. Decoupled multi-loop aquaponics systems, in which the aquaculture and hydroponics subsystems are running autonomously, proved that they can keep up with the productivity of state-of-the-art hydroponics systems or even outscore them. Yet, a problem of such decoupled aquaponics systems was that plants require a high nutrient concentration, whereas fish prefer rather a clean water. In practice, the opposite is happening as the nutrients are added to the aquaculture units through the feed. This paper optimizes a recent approach showing that desalination technologies, such as reverse osmosis, can play an important role in reversing the concentrations within such systems without killing beneficial plant growth–promoting rhizobacteria thermally. The proposed integrated systems approach has the potential to make both periodical nutrient and water discharges and excessive fertilizer supplementation obsolete that would otherwise be necessary to maintain good water quality for the fish and an optimal nutrient solution for the plants.