Urban aquaponics farming and cities- a systematic literature review

Is Aquaponics Beneficial in Terms of Fish and Plant Growth and Water Quality in Comparison to Separate Recirculating Aquaculture and Hydroponic Systems?

Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and specific growth rates were higher, and the feed conversion ratio was lower than those grown in RAS. In spinach, there were no significant differences in growth between aquaponic and hydroponic treatments. The concentration of GSM was significantly higher in the roots and MIB in the shoots of spinach grown in aquaponics than in hydroponics. In fish, the concentrations of MIB did not differ, but the concentrations of GSM were lower in aquaponics than in RAS. The onset of nitrification was faster in the aquaponic system than in RAS. In conclusion, spinach grew equally well in aquaponics and hydroponic systems. However, the aquaponic system was better than RAS in terms of onset of nitrification, fish growth, and lower concentrations of GSM in fish flesh.

Can Reclaimed Water Be Used for Sustainable Food Production in Aquaponics?

Aquaculture is a technology used for the production of animal protein but produces a great amount of waste that decreases productivity and adversely affects the environment. Sedimentation and filtration have been used for the treatment of the suspended fraction of these wastes although dissolved substances like nutrients can be an asset. Therefore, the management of aquaculture waste remains a challenge. Aquaponics is a technology that can eliminate dissolved N and P from aquaculture systems as they serve as nutrients for plants, which are absorbed through the roots and are incorporated into their tissues. Several reports and studies exist on the benefits of aquaponic systems for the combined production of plants and aquatic organisms and its advantages in terms of economics and environmental protection. The great majority of the studies use the wastewater from the aquatic production tanks as a source of nutrients for plants production. However, domestic or municipal wastewater is a resource that has been used extensively in other production systems such as conventional agriculture and aquaculture, yet its potential as a source of water for aquaponics has not been established. The current analysis hypothesizes that reclaimed water can be used for aquaponics. Despite the extensive use of reclaimed water in agriculture and aquaculture and the low risk to human health when properly managed, there are no academic studies that have tackled this issue. In order to overcome the generalized mistrust of the public in consuming crops irrigated with reclaimed water or fish growing in reclaimed water, it is recommended that only ornamental fish and plants would be cultivated by this method. There is an urgent need for studies to verify the safety and advantages of such cultivation technique. Finally, it is necessary to establish guidelines for the responsible use of reclaimed water in aquaponics.