Improving nitrogen recycling in an aquaponics system by adding a composting process from fish sludge

Abstract

The goal of this research is to recover nutrients from wastewater sludge and recirculate them as organic fertilizer in aquaponics systems. Improving the sustainability of aquaponics by increasing economic and environmental efficiency. In this study, an improved aquaponics system was developed including a fish pond, biological reactor, growing bed, and composting site. In addition, an ecological floating bed is placed on the surface of the fish pond to absorb nutrients in the fish pond. After a farming cycle lasting more than 3 months, the biomass of Cyperus haspan is harvested and mixed with fish sludge from the biological reactor tank to produce organic fertilizer. The nitrogen and carbon balance model was established to evaluate the nutrient recovery efficiency of the aquaponics system. The results indicate that nutrient recovery from fish sludge can also address the problem of nutrient deficiency faced by aquaponics systems and reduce the costs associated with the purchase of additional nutrients. Besides, 32 - 45% of N originating from fish feed is assimilated into plant biomass. It is estimated that about 35-45% of unaccounted N is lost to the atmosphere, the remaining 20-25% into wastewater, and 0.8-3% into solid waste. The average weight of fish harvested in the system is 531±94.2 g/fish with a survival rate of 80%. Plant biomass in three harvests reached 1.8 to 2 kg/m2.