## 2 Proposed Smart Farm Structure: Overall System--Inflatable Aeroponic Enclosed Smart Farm
### Water Circulation System '2, 3, 4'
#### 2.2.3 Drainage Manager '4'  
The Drainage Manager system is a critical component for handling water that has passed through plant roots, incorporating a filtration mechanism to remove root debris and other contaminants [44]. The reclaimed solution might contain undigested organic materials from the initial misting process, which can promote the growth of anaerobic bacteria, leading to solution contamination and unpleasant odors. To address this issue, this study utilizes a combination of a biofilter, capable of decomposing organic material, and a mechanical filter. This integrated filtration system effectively enhances the removal of organic compounds, thereby significantly reducing water contamination levels and providing an efficient solution for maintaining the purity of the irrigation solution.  
To maximize the effectiveness of the biofilter, it is crucial to design the system in such a way that it maximizes contact time between the water and the microbes. As depicted in Figure 6, the biofilter is designed to make the drainage flow through the longest possible path inside the filter box, thereby maximizing the contact period between the organic material and the microbes. This is achieved by filling a vertical circulating filter box with a porous filtration medium, integrating it with bacterial filter media and a six-layer filtering system to enhance fluid dynamics and facilitate the efficient removal of organic matter. The actual installation is shown in Figure S7. A small submersible pump installed at the bottom of the filter box continuously circulates the drainage, reducing the concentration of organic material in the water while promoting microbial life and reproduction. This design of the biofilter effectively utilizes the biological activity of microbes during the water purification process, contributing to the removal of organic substances within the nutrient solution and improving water quality.  
Figure 6: Design structure of the biofilter and conceptual diagram of biofilter implementation. The **left** image depicts the internal layout of the biofilter, showing the flow of drainage and the action of bio microorganisms within the system. The **right** image provides a detailed view of the multi-layered filtration system, including a 6-layer filter, bacterial filter material, and the biofilter itself.  
The nutrient solution circulation system necessitates continuous and rapid water cycling; however, the biofiler's processing is inherently time-consuming. Within this system, the mixed solution can become contaminated during the circulation process, often necessitating complete disposal of the contaminated solution. To address this, the study proposes a new Drainage Manager that omits path '4-2' from Figure 1, allowing for the immediate re-spraying of the collected water and thus reducing the volume of water in circulation. This innovative Drainage Manager employs a centrifugal spraying method that does not collect the residual water directly after spraying but re-sprays it immediately, thereby reducing the volume of waste solution. The centrifuge uses a spinning propeller to draw water and project it onto a separation screen, creating particles ranging from 20 to 100 \(\upmu\)m in size.  
To validate the functional performance of this system, a vertical cultivation platform measuring 2 m in height, 6 m in width, and 35 cm in depth was constructed as shown in Figure 7, with a central centrifugal sprayer installed for the cultivation experiments. The experiment involved growing 250 leafy vegetables for three weeks, approximately 20 days post-seeding. The data obtained from this experiment demonstrated that this drainage management method could reduce the amount of water recaptured while ensuring normal plant growth, thus confirming its potential efficacy.