Performance comparison of down-flow hanging sponge reactor and moving bed bioreactor for aquaponic systems

Aquaponics require high-quality water purification for the high and stable production of fish and vegetables. This study investigated the performance of a down-flow hanging sponge (DHS) reactor and a moving bed bioreactor (MBBR) in an Acipenser ruthenus–Lactuca sativa aquaponic system. At high fish density conditions, the NH₄⁺-N in the DHS-aquaculture tank was maintained as low as 0.38 ± 0.26 mg-N·L⁻¹ compared with the MBBR-aquaculture tank despite an effective volume of one-fifth. Additionally, the DHS-aquaponic system produced greater amounts of lettuce (1075.23 g) and longer plants (21.70 ± 1.36 cm) in comparison to the MBBR system (842.78 g and 17.02 ± 2.2 cm). This study showed that a DHS system effectively reduces ammonium nitrogen concentrations, stabilizes nitrogen levels in water, and enhances the ecological health of hydroponic systems. Therefore, the DHS system not only improves agricultural production efficiency but also promotes sustainable agricultural development.