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Mesocosm-Scale Constructed Wetland Design for Wastewater Treatment
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Controlling harmful algal blooms in constructed wetlands: A hydrodynamic cascade driven by engineered microtopography
Jiaqi Liu1, Xiaoyi Xu2, Yongbo Jiang3
1School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China.
Journal of Environmental Management
|April 14, 2026
Summary
Engineered microtopography in constructed wetlands creates varied water flow, suppressing harmful algal blooms (HABs). This nature-based solution shifts phytoplankton from harmful cyanobacteria to beneficial diatoms, improving water quality.
Area of Science:
- Environmental Engineering
- Aquatic Ecology
- Water Resource Management
Background:
- Constructed wetlands are vital for eutrophication control but struggle with harmful algal blooms (HABs) due to stagnant flow and cyanobacterial dominance.
- Homogeneous flow paths in traditional wetlands limit their effectiveness in mitigating HABs, necessitating innovative solutions.
Purpose of the Study:
- To introduce and evaluate a novel engineered microtopography design for constructed wetlands to physically suppress HABs.
- To investigate the hydrodynamic mechanisms and water quality impacts of microtopography on algal communities.
Main Methods:
- Integrated computational fluid dynamics (CFD) modeling and year-long field monitoring.
- Analysis of water quality parameters (TN, TP, CODMn, DO) and phytoplankton functional groups.
- Structural equation modeling (SEM) to determine causal relationships between physical structure, hydrodynamics, and algal shifts.
Main Results:
- Engineered microtopography created heterogeneous flow regimes, including low-velocity vortices and high turbulence zones.
- These hydrodynamic patterns enhanced algal settling, disrupted cyanobacterial aggregation, and altered water quality parameters.
- A significant shift in phytoplankton from high-risk cyanobacteria to low-risk diatoms and cryptophytes was observed.
Conclusions:
- Microtopography-induced flow heterogeneity is a primary driver for reducing HABs by altering phytoplankton communities.
- The proposed 'Hydrodynamic-Template Cascade Model' offers a predictive, mechanism-based strategy for sustainable wetland design.
- This approach enables proactive HAB control in constructed wetlands without chemical intervention.
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