OVERVIEW--Compact Biological Abyss (CBA)

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To achieve the function of engineered bacteria adsorbing and settling Ulva prolifera spores in marine environments, we designed a small, field-deployable filter hardware— Compact Biological Abyss (CBA). CBA is manufactured using 3D printing technology and aims to address the Ulva prolifera outbreak issues in the shallow shoal areas of northern Jiangsu. By integrating a coarse filtration system and a biological filtration system, the device can effectively filter spores from seawater while ensuring stable attachment and functional performance of the engineered bacteria.

Fig1. Hardware Cartoon Diagram

Overall Hardware Design

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The hardware is divided into two main modules: the coarse filtration system and the biological filtration system. The coarse filtration system includes a filter box and a sand separation device, primarily used for initial removal of adult algae, sediment, and large particulate impurities. The biological filtration system centers on a minimal surface moving bed biofilm reactor (MBBR), which carries the engineered bacteria for spore adsorption. The two modules are connected via magnetic attachment devices, facilitating assembly, disassembly, and maintenance. The interior of the entire hardware enclosure is maintained in complete darkness to accommodate the engineered bacteria's light-induced suicide mechanism. Seawater carrying Ulva prolifera spores enters the coarse filtration system, is purified by the sand separation device, and then flows into the biological filtration system. The engineered bacteria in the minimal surface MBBR adsorb spores from the seawater, and finally, clean seawater is discharged via a pump. For the detailed design ideas and process, please refer to the section four.

Fig2. Overall Hardware Exploded View.

Video 1: Display of overall hardware assembly process.

Video 2 : Hardware Experiment Demonstration Video.

The hardware is manufactured using fused deposition modeling (FDM) 3D printing technology, with polylactic acid (PLA) as the material. PLA is derived from renewable resources such as corn starch and is considered an environmentally friendly alternative to traditional plastics, suitable for marine deployment. PLA has high biocompatibility, and its surface roughness promotes microbial attachment. Additionally, the layer grooves produced during the FDM printing process provide "shelters" for the engineered bacteria, aiding in biofilm formation. In terms of printer parameters, we selected a layer height of 0.20mm.

Coarse Filtration System

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Seawater in the shallow shoals of northern Jiangsu contains sediment, adult algae, and large particulate debris, which may cause blockages. To mitigate risks and ensure stable operation, we designed the coarse filtration system.

Coarse Filter Box

The coarse filter box is positioned on the outer periphery of the system, consisting of four units, with internal multi-layer filter plates of graduated pore sizes (10 mm, 5 mm, and 2.5 mm) to progressively remove large particulate impurities. The multi-directional placement of the filter box was inspired by discussions with the Southern University of Science and Technology team at the CCiC conference, ensuring multi-directional water intake to adapt to changes in seawater flow direction.

Fig3. Coarse Filter Box Model Diagram.

Fig4. Coarse Filter Box 3D Printed Physical Image.

Sand Separation Device

For the issue of high sediment content, we drew inspiration from the design principles of the ancient Chinese Dujiangyan Irrigation System ^[1]. Its core design—the "Fish Mouth" diversion dike (a fish-mouth-shaped diversion structure)—ingeniously utilizes fluid dynamics principles to achieve automatic diversion and sediment discharge, avoiding sediment accumulation that interferes with irrigation and flood control. Specifically, the "Fish Mouth" divides the Minjiang River flow into two branches: the Inner River and the Outer River. The Inner River is designed as a narrow and deep channel, which results in faster water flow and greater kinetic energy, facilitating the transport of fewer sediment particles and thus delivering relatively clear water for irrigation and water supply; the Outer River, on the other hand, is designed as a wide and shallow channel, with slower water flow and less kinetic energy, allowing sediment particles to settle and discharge under the effects of gravity and friction, preventing entry into the main irrigation system. Additionally, Dujiangyan cleverly simulates the curved morphology of natural river channels, further enhancing sediment separation through centrifugal force generated in bends: at the bend, the outer side of the water flow is faster, carrying heavier sediment particles that deviate outward due to inertia and deposit, while the inner side water flow remains relatively pure.

Based on this principle, we developed a sediment separation device: the core structure of the device simulates the "Fish Mouth" diversion, divided into an inner channel (narrow and deep design) and an outer channel (wide and shallow design). When water flow with high sediment content enters the device, it first undergoes preliminary separation through the diversion port at the entrance, with the high-speed water flow in the inner channel preferentially guiding the clear water body to flow, while the low-speed shallow layer in the outer channel promotes sediment settlement. At the same time, we introduced curved paths simulating natural river channels, utilizing the centrifugal force principle at the bends to generate radial acceleration during turning, prompting larger particle size sediment to be thrown outward to the bend's outer side, thereby further improving separation efficiency.

Fig5. Sand Separation Device Model Diagram.

Fig6. Sand Separation Device 3D Printed Physical Image.

We conducted flow diversion tests and sand separation tests on the sand separation device. Results indicate significant diversion effectiveness: when flow is high, outer channel water level exceeds inner channel; when flow is low, inner channel water level surpasses outer channel. Although sand separation effects are not pronounced, experiments demonstrate the device possesses some sand separation capability, with inner channel sediment levels lower than outer channel. Moving forward, we aim to further enhance sand separation efficiency by optimizing the device's bending angle and inner-to-outer channel ratio through software simulation.

Fig7. Sand Separation Device Test Results Image.

Other components of the coarse filtration system.

Fig8. Coarse filtration system body housing、Coarse filtration system body capping、Coarse filter box housing、Coarse filter box closure Model Diagram.

Fig9. Coarse filtration system body housing、Coarse filtration system body capping、Coarse filter box housing、Coarse filter box closure 3D Printed Physical Image.

Biological Filtration System

Spherical Gyroid MBBR

Engineered bacteria require efficient carriers to maximize contact with seawater. Traditional MBBR (Moving Bed Biofilm Reactor) systems suffer from limitations such as low surface area-to-volume ratio (SAVR), uneven flow distribution, and easy biofilm detachment ^[2]. To overcome these, we introduce triply periodic minimal surfaces (TPMS), a mathematical structure with zero mean curvature, widely used in architectural design and materials science. This minimal surface originates from differential geometry and features unique zero mean curvature properties, ensuring minimal surface energy and thus providing a highly stable geometric framework, which performs exceptionally well in bioengineering applications ^[3].

We selected the Gyroid-type TPMS to construct spherical Gyroid MBBR, where its helical interconnected channels significantly enhance SAVR, promoting uniform fluid distribution and biofilm growth. Compared to traditional media, the Gyroid structure's high SAVR greatly increases the contact area between engineered bacteria and seawater, thereby improving pollutant degradation efficiency. At the same time, the saddle-shaped curvature and interconnected pores not only promote uniform fluid distribution and reduce turbulent dead zones but also optimize fluid dynamics: the smooth transitions of the minimal surface reduce flow resistance, avoiding common local blockages and inefficient areas in traditional MBBR. Additionally, the surface provides multi-scale "shelters," and through its continuous curved morphology, it reduces shear force impacts on the biofilm, making the biofilm more stable and durable, even in high-flow environments. This benefits from TPMS's self-supporting structure, which requires no additional supports to achieve uniform stress distribution, further minimizing detachment risks.

The advantages of TPMS are also evident in sustainability and adaptability: although the initial cost of 3D printing such structures is higher, the lifecycle cost is low, and the structures are reusable. Their high mechanical strength and chemical stability stem from the geometric optimization of the minimal surface, making them corrosion-resistant and wear-resistant in marine environments, with stronger mobility.

Fig10. Gyroid MBBR Model Diagram.

Fig11. Gyroid MBBR 3D Printed Physical Image.

We conducted biofilm attachment and suspension experiments on spherical Gyroid MBBR, with results shown in the figure. By co-culturing engineered bacteria with traditional MBBR and spherical Gyroid MBBR, we observed that spherical Gyroid MBBR exhibited a certain degree of biofilm attachment effect. For specific experiments on the adsorption of spores by engineered bacteria, please refer to the experimental section. Additionally, we tested the suspension performance of spherical Gyroid MBBR of different sizes in seawater, and the results showed that the 27 mm diameter spherical Gyroid MBBR could achieve a near-suspended state after mild disturbance (while carriers of other sizes tended to float or sink). The aforementioned spherical Gyroid MBBR were all generated using a density parameter of 6.00 (a dimensionless value controlling the mesh generation fineness) and an isosurface value of 0.085 (defining the threshold C for the implicit function F(x, y, z)), produced via software formulas; their thickness was automatically determined by the 3D printer. In the future, we plan to adjust the relevant parameters of spherical Gyroid MBBR to explore optimized conditions more suitable for biofilm attachment.

Fig12. Gyroid MBBR Test Results Image

During the hardware design process, we consulted Professor Min Chen from the School of Advanced Technology at Xi'an Jiaotong-Liverpool University. Professor Chen emphasized that hardware design should focus on multi-scale and multi-gradient integration to optimize structural performance and adaptability. He suggested exploring the combination of various minimal surfaces (such as Gyroid, Schwarz P, and Neovius) with the hardware to build functionally diverse main modules, thereby significantly enhancing the device's migratability and application potential in different environments.Therefore, we have compiled a summary table on the transferability of triply periodic minimal surfaces, for future iGEM teams to reference, draw inspiration from, and apply in practice ^[4].

Structural Characteristics and Applications of TPMS

Triply Periodic Minimal Surface Structures

Expand/Collapse All

Gyroid (G) ▼

TPMS Structure

• Spiral interconnected channels forming a continuous "sponge" network.

• high symmetry, three-dimensional periodic repetition.

Key Functional Effects

• High SAVR: Maximizes surface exposure, promoting attachment and diffusion.

• Excellent flow mixing: Spiral paths reduce dead zones, enhancing mass transfer efficiency.

• Balanced mechanical strength: Flexible framework, resistant to shear but prone to deformation.

• Efficient heat transfer and turbulent kinetic energy: Smooth surfaces generate high turbulent kinetic energy, promoting heat exchange and energy absorption.

Potential Applications

• Wastewater treatment: As MBBR carriers, improving biofilm growth and pollutant removal.

• Biomedical: Bone scaffolds or tissue engineering, promoting cell migration and nutrient transport.

• Energy: Fuel cell electrodes or heat exchangers, optimizing gas/liquid flow.

• Architecture: Lightweight insulation materials, simulating natural ventilation structures.

Schwarz Primitive (P) ▼

TPMS Structure

• Cubic unit saddle surfaces forming regular interconnected pores.

• simple symmetry.

Key Functional Effects

• Medium SAVR: Uniform surface distribution, suitable for load balancing.

• High permeability: Straight channels promote rapid flow and filtration.

• Excellent heat/mass transfer: Low resistance, high energy efficiency.

• High stiffness ratio: Suitable for bending and impact absorption.

Potential Applications

• Energy: Solar collectors or catalyst supports, increasing reaction rates.

• Materials science: Porous ceramics or metal foams for lightweight high-strength composites.

• Environmental engineering: Air purification filters, capturing particulate matter and pollutants.

• Mechanical applications: Flexure hinges, improving stiffness and stiffness ratio; sandwich panel cores, providing the highest strength-to-weight ratio.

• Biomedical applications: Bone defect fillers, controlling mechanical properties.

Schwarz Diamond (D) ▼

TPMS Structure

• Diamond-like grid structure, resembling a diamond crystal.

• High curvature variation.

Key Functional Effects

• High SAVR: Complex grids providing multi-scale pores.

• Superior mechanical strength: Rigid framework, strong resistance to compression/impact.

• Self-supporting: Minimal material usage, high structural stability.

• Efficient heat transfer: Minimal flow separation, smooth surfaces enhancing heat exchange efficiency.

• Catalytic support: High contact area, promoting chemical reactions.

Potential Applications

• Biomedical: Implantable devices or drug delivery systems, utilizing strength to support bone regeneration.

• Aerospace: Lightweight structural components, reducing weight while maintaining strength.

• Energy storage: Battery separators, improving ion transport and durability.

• Thermal applications: Heat exchangers, improving thermal performance and reducing wall thickness.

• Mechanical applications: Turbine blades, optimizing lightweighting, stress, and deformation.

I-Wrapped Package (I-WP) ▼

TPMS Structure

• Body-centered cubic symmetric "wrapped" network, forming highly interconnected channels.

• Similar to an extended lattice, high symmetry.

Key Functional Effects

• High SAVR: Provides multi-scale pores, promoting diffusion and attachment.

• Controllable stiffness and permeability: Excellent linear elastic phase, suitable for energy absorption and mass transfer control.

• Suitable for bone integration: Large unit cell regions enhance colonization and vascularization.

• Thermal/chemical stability: Smooth surfaces optimizing flow and reaction efficiency.

Potential Applications

• Biomedical: Bone scaffolds or implants, providing suitable regions for bone colonization and promoting osseointegration.

• Energy: Heat exchangers or battery components, utilizing bandgaps to optimize energy storage.

• Mechanical applications: Vibration isolators or lightweight structures, utilizing linear elasticity for impact absorption.

• Chemical applications: Catalyst carriers or microreactors, improving reaction rates and conversion efficiency.

Neovius ▼

TPMS Structure

• Extended cubic network, similar to an extended Schwarz P.

• Denser channels.

Key Functional Effects

• Extremely high SAVR: Dense pore network, maximizing contact area.

• Enhanced diffusion control: Fine channels suitable for microscopic transport and separation.

• Thermal stability: Uniform curvature distribution, resistant to high temperatures/corrosion.

• Controllable pore size: Promotes bone colonization and vascularization.

Potential Applications

• Chemical engineering: Catalytic reactors, supporting efficient chemical synthesis.

• Nanotechnology: Nanoparticle templates for drug encapsulation or sensors.

• Architecture: Acoustic/insulation panels, optimizing energy absorption and diffusion.

• Biomedical applications: Osseointegration scaffolds, providing suitable regions for bone colonization; simulating cortical/trabecular bone.

• Mechanical applications: Energy absorbers or vibration isolators, utilizing linear elastic phase.

Table 1: Key Functions and Potential Applications of Common TPMS Structure Types (such as Gyroid, Schwarz P, Schwarz D, I-WP, and Neovius).

Fig13. Photo with Professor Min Chen. Professor Min Chen’s research focuses on the structure optimization, reliability analysis, computational mechanics and product design.

Other components of the biological filtration system.

Fig14. Network structure of biological filtration system、Biological filtration system body housing、External magnetic device、Internal magnetic device Model Diagram.

Fig15. Network structure of biological filtration system、Biological filtration system body housing、External magnetic device、Internal magnetic device 3D Printed Physical Image.

Implementation of hardware

The initial focus of the hardware was on modifying the buoys of the Qingdao interception nets. However, surveys by the HP (Human Practices) group revealed that Ulva prolifera spores are primarily released in the shallow shoals of northern Jiangsu, attaching to laver raft frames. Consequently, the hardware application scenario shifted to the shallow shoals of northern Jiangsu, though the specific placement method remained unknown. Specific investigation process can be found in iHP.

On September 6, 2025, we traveled to Lianyungang for on-site surveys and interviewed Mr. Sun Yutian, who has 30 years of experience in laver cultivation, to learn detailed information about the cultivation area frameworks. On the sea surface, the cultivation areas are secured by erecting support poles, with the outermost perimeter using ropes equipped with buoys as the framework, forming approximately 30 mu (about 5 acres) of laver cultivation zones. Inside, these are lined with laver curtains (another net-like structure woven from ropes) that carry laver seedlings. Each year, fishermen retrieve these laver curtains, reseed them, and place them back into the offshore frameworks to continue cultivation. During this period, Ulva prolifera grows on the rope areas without laver seedlings, affecting laver yields. Although local fishermen use traditional methods to remove Ulva prolifera from the laver curtains, they still face recurring invasions of Ulva prolifera every year.

Fig16. Lianyungang Interview Image.

Fig17. Laver Raft Frame Image.

Lianyungang's laver cultivation is located in the open sea. Due to our lack of access permits, we were unable to board fishermen's boats for on-site inspections. Therefore, we commissioned local fishermen to take photos and videos of the laver raft frames while at sea, allowing us to obtain firsthand data.

Ultimately, we decided to adopt a rope connection method, placing the hardware at intervals around the perimeter of the cultivation areas, while adding sponges to ensure the water inlets are level with the sea surface, adapting to tidal changes. This design optimizes the hardware's buoyancy and adaptability: the rope connections allow the hardware to move flexibly with the waves, reducing the risk of damage; the sponge buffering mechanism maintains a stable water level at the inlets, ensuring continuous contact between the engineered bacteria and seawater, enabling efficient operation even in environments with significant tidal fluctuations.

Hardware Design Cycle

Our hardware development process follows the DBTL engineering cycle advocated by iGEM, evolving from a broad concept into a targeted, functionally optimized solution through continuous iteration and learning.

Cycle: Design Iteration

Cycle 1

Design:

After confirming that governance should focus on northern Jiangsu shallow shoals, we initiated the first version of the hardware design. Discussions with the modeling team revealed that arranging engineered bacteria in a checkerboard pattern is more conducive to their aggregation and functional performance; meanwhile, to extend the contact time between seawater and bacteria, water flow speed needs to be minimized to optimize adsorption efficiency. For details, see the Ag-Nb module on the model page.

Build:

Based on this, we designed biological plates embedded with a checkerboard structure and serpentine pipes to slow flow speed. By alternating biological plates and serpentine pipes, we built the first prototype of the hardware.

Fig18. First Edition Hardware Design Diagram.

Test/Evaluate

We gathered opinions from relevant individuals and engaged in in-depth discussions with other teams at the CCiC conference to evaluate the design's feasibility and potential issues.

Learn:

We found that the flat design of the biological plates, under laminar flow effects, resulted in lower overall biofilm adsorption efficiency for spores; additionally, the high sediment content in northern Jiangsu shallow shoal seawater easily caused blockages in serpentine pipes. Therefore, we comprehensively improved and optimized the hardware design.

Cycle 2

Design:

To address the low adsorption efficiency, we introduced minimal surface structures, combining them with moving bed biofilm reactors (MBBR) to design a spherical Gyroid MBBR. This structure, with its high surface area-to-volume ratio (SAVR) and optimized saddle-shaped curvature, not only significantly increases bacterial attachment area but also promotes uniform contact between engineered bacteria and seawater, thereby enhancing overall spore adsorption efficiency. Meanwhile, to alleviate sediment blockages, we incorporated the engineering principles of Dujiangyan's "fish mouth" structure into the hardware design for automatic sand separation.

Build:

We used modeling software to design and build prototypes of the spherical Gyroid MBBR and sand separation device, ensuring structural precision and printability.

Test:

The experimental team conducted engineered bacteria cultivation tests and spore adsorption measurements on the spherical Gyroid MBBR, as well as sand discharge efficiency experiments on the sand separation device, to verify performance in simulated seawater environments.

Learn:

Results showed that the spherical Gyroid MBBR exhibited biofilm attachment characteristics, and the sand separation device achieved the sediment separation effects. Based on these findings, we plan to further optimize device parameters to enhance overall efficiency and stability.

Hardware Advantages

Our hardware design demonstrates significant advantages in economy, migratability, innovation, and sustainability, which not only enhance its practical value but also align with iGEM's requirements for scalability and environmental friendliness in engineering solutions. The following is a detailed elaboration of each advantage:

• Economy: 3D printing technology is currently highly mature, so all components of our designed hardware can be easily replicated by other teams, offering good reproducibility and scalability. Using FDM 3D printing technology and PLA material, the cost of the entire hardware unit is controlled within 100 RMB (14＄) based on Bambu Lab software estimates, including materials and printing costs (see the table below). Compared to traditional metal or injection-molded filters, our design significantly reduces manufacturing expenses, facilitating large-scale production, promotion, and iteration.

  Video 4: FDM 3D Printing Process Video. The 3D printer model we use is the Bambu Lab P1S.

  
  

  Component	Material	Filament Usage (g)	Estimated Cost (CNY)	Printing Time (h)	Quantity	Total cost(CNY)
  Coarse filter plate 2.5mm	PLA Basic	5.90	0.15	23m25s	4	0.60
  Coarse filter plate 5.0mm	PLA Basic	4.51	0.11	28m21s	8	0.88
  Coarse filter plate 10.0mm	PLA Basic	4.47	0.11	16m5s	4	0.44
  Coarse filter box closure	PLA Basic	14.55	0.36	24m32s	4	1.44
  Coarse filter box housing	PLA Basic	48.81	1.22	1h25m	4	4.88
  Sand separation device	PLA Basic	20.43	0.51	37m27s	4	2.04
  Coarse filtration system body housing	PLA Basic	170.70	4.27	3h33m	1	4.27
  Coarse filtration system body capping	PLA Basic	110.93	2.77	2h4m	1	2.77
  Network structure of biological filtration system	PLA Basic	48.48	1.21	2h59m	1	1.21
  Biological filtration system body housing	PLA Basic	237.38	5.93	5h18m	1	5.93
  External magnetic device	PLA Basic	21.55	0.54	42m49s	2	1.08
  Internal magnetic device	PLA Basic	18.85	0.47	39m15s	2	0.94
  Spherical Gyroid MBBR	PLA Basic	55.21 (Includes support material)	2.03	3h9m	8	16.24
  Total				≈19.8h		42.72

  Table 2: Hardware Cost Price List. The prices listed above account only for filament costs. Printer operation is estimated at ¥2 per hour, and when factoring in other miscellaneous expenses, the total hardware cost comes to approximately ¥100.

• Versatility : The modular design (magnetic connections and detachable components) allows easy adaptation to different marine environments, such as expanding from northern Jiangsu shallow shoals to other algal bloom-prone areas. The universality of the TPMS structure makes it transplantable to wastewater treatment plants, industrial wastewater processing, or freshwater ecological restoration applications, for example, by modifying Gyroid surface parameters to optimize specific pollutant adsorption.

• Innovation: The hardware cleverly integrates the sand diversion principle of ancient China's Dujiangyan with TPMS structures from modern differential geometry, enhancing the long-term stability of engineered bacteria through multi-scale shelters, embodying the perfect integration of mathematical aesthetics and bioengineering.

• Sustainability: Selecting PLA as the printing material, which is environmentally friendly and biodegradable, is suitable for marine deployment and avoids long-term plastic pollution. The sand separation device reduces sediment blockages, extending service life, and The passive design of the spherical Gyroid MBBR enables low energy consumption by eliminating the need for continuous stirring, thereby significantly reducing the carbon footprint. Overall, the hardware supports a circular economy model, is recyclable and reusable, and aligns with UN Sustainable Development Goal (SDG 14: Life Below Water).

• User-Friendliness: Magnetic assembly and rope fixation simplify the deployment process, requiring no professional tools, allowing fishermen to complete installation in 5 minutes. The multi-directional water intake design of the coarse filtration system adapts to tidal changes, reducing maintenance frequency.

Conclusions and Future Outlook

Conclusions

In summary, CBA, as a small, on-site deployable 3D-printed filter hardware, can preliminarily achieve coarse filtration and sand separation functions. At the same time, we have verified that biofilms can attach to spherical Gyroid MBBR, and its fully dark internal environment is suitable for the survival of engineered bacteria, thereby demonstrating the potential of this hardware to assist engineered bacteria in adsorbing Ulva prolifera spores in the shallow shoal areas of northern Jiangsu.

Future Outlook

Currently, drainage primarily relies on water pumps, while power supply presents certain challenges. To address this, we plan to introduce solar panels to achieve energy self-sufficiency for the system. Simultaneously, we are exploring the adoption of a siphon system to replace the reliance on pumps during water discharge through purely physical means, thereby simplifying the hardware structure.

Regarding key component optimization, we will combine computational fluid dynamics simulations with field testing to perform data-driven optimization of the sand separation system's bend parameters and inner-to-outer channel ratio, thereby enhancing sand separation efficiency. For the Spherical Gyroid MBBR, we will optimize its surface thickness and pore density to enhance biofilm attachment. We will introduce a “multi-gradient” concept, arranging combinations of different porosities within the same minimal surface structure to create a medium with gradient adsorption and filtration capabilities. Additionally, we will adopt a “multi-scale” approach, systematically studying the performance of various minimal surface structures across different scales to expand the hardware's applicability across diverse scenarios.

To further enhance system maintainability, we will deploy a multi-parameter sensor system. Integrating units for turbidity, temperature, and other parameters, this system dynamically monitors pipeline blockages and biofilm activity, enabling precise assessment of operational health and laying the foundation for remote monitoring and intelligent management.

Long-term goal: The integrated system composed of hardware and engineered bacteria can be deployed on a large scale in the shallow shoals of northern Jiangsu, reducing the impact of Ulva prolifera outbreaks on local laver cultivation and alleviating the Ulva prolifera bloom problem in Qingdao.

References

[1]Li, K. and Xu, Z. (2006) ‘Overview of Dujiangyan Irrigation Scheme of ancient China with current theory’, IRRIGATION AND DRAINAGE, 55(3), pp. 291–298. doi:10.1002/ird.234.↩︎

[2] di Biase, A. et al. (2019) ‘Moving bed biofilm reactor technology in municipal wastewater treatment: A review’, Journal of Environmental Management, 247, pp. 849–866. doi:10.1016/j.jenvman.2019.06.053.↩︎

[3] Wallat, L. et al. (2022) ‘Computational Design and Characterisation of Gyroid Structures with Different Gradient Functions for Porosity Adjustment’, Materials, 15(10), p. 3730. doi: 10.3390/ma15103730.↩︎

[4] Jiawei Feng;Jianzhong Fu;Xinhua Yao;Yong He (2022) ‘Triply periodic minimal surface(TPMS)porous structures:from multi-scale design,precise additive manufacturing to multidisciplinary applications’, International Journal of Extreme Manufacturing, 4(2), pp. 1–31. doi: 10.1088/2631-7990/ac5be6.↩︎