A new and improved aquaponics system model for food production patterns for urban architecture

Productive cities are one of the most important ways to achieve urban sustainable development. In the comprehensive production function, food production is the most basic function and should be defined as a priority. Considering the characteristics of buildings and the limitations of the urban environment, aquaponics is a safe and healthy green technology that protects the ecological environment and that has high potential to combine urban buildings and plant cultivation technology. Research on aquaponic systems has become increasingly mature, but some new problems that cannot be ignored, such as low nitrogen utilization efficiency, high aeration cost and noise problems, and unreliable water quality. In this study, a new aquaponics system model (photosynthesis reoxygenation aquaponics, PRO-AP) was proposed, and it was expected that the structure of the system can be adjusted by adding macroalgae to improve the existing problems in aquaponics. An experiment was conducted to preliminarily explore the feasibility of the proposed mode of operation. Spirogyra was added to the aquaponics system, and the DO, pH, TDS, EC, ammonia nitrogen and removal of the key nutrients from the systems were monitored during the operation. The results showed that the dissolved oxygen content in the system increased markedly and that the pH drop caused by nitrifying bacteria could be balanced when Spirogyra was irradiated with effective light. In addition, Spirogyra played a certain role in biofiltration in the aquaponic system, which reduced the values of TDS and EC, the contents of NH₄⁺, NO₃⁻ and PO₄³⁻ also decreased, and the nitrite content first increased and then decreased after a period of time. Finally, under the ratio of fish and vegetables in this experiment, the existence of Spirogyra did not create a negative image of the yield and root system of vegetables in aquaponics systems. The results showed that the aquaponic system with macroalgae has a stronger self-regulation ability. PRO-AP is an effective method in urban food production and is a very promising mode of production in the sustainable development of productive cities.