Design and evaluation of a community-scale bioretention system for urban stormwater management and pollutant removal under tropical climate conditions

Project Abstract

Bioretention systems offer a nature-based solution to urban stormwater management by combining filtration, plant uptake, and microbial processes to remove pollutants; however, performance under tropical climate conditions with high rainfall intensity, elevated temperatures, and diverse pollutant loads remains underexplored. This study designs, implements, and evaluates a community-scale bioretention cell in a tropical urban setting to quantify hydrological performance, pollutant removal efficiency, resilience to climate variability, and maintenance requirements. The research employed a mixed-methods approach, including hydrological modeling, in-situ water quality monitoring, and agro-ecological assessments of selected plant species and soil media. A full-scale bioretention system was constructed adjacent to a low-lying urban drainage outlet to capture runoff from a 1.2 ha catchment, with an influent storm event database spanning two monsoon seasons and an extended dry season. Instrumentation tracked inflow and outflow hydrographs, groundwater levels, temperature, pH, dissolved oxygen, sedimentation rate, and moisture content across media layers. Water quality analysis targeted nutrients (N, P), heavy metals (Zn, Cu, Pb, Fe), suspended solids, biological oxygen demand, chemical oxygen demand, and emerging contaminants such as microplastics and pharmaceuticals. Laboratory and field assays characterized the media’s hydraulic conductivity, porosity, cation exchange capacity, and biodegradation potential. A tiered analytical framework assessed process pathways including infiltration, adsorption, plant uptake, microbial nitrification-denitrification, and phytoremediation under tropical plant physiology constraints. Spatial design optimization explored media depth, porosity, and plant community composition to maximize pollutant attenuation while maintaining safe hydraulic conveyance. Results indicate that the bioretention system achieved mean removal efficiencies of 65–82% for total nitrogen, 58–76% for total phosphorus, and substantial reductions in suspended solids, with higher performance during periods of intense rainfall due to enhanced dilution and increased infiltration. Heavy metals exhibited variable removal linked to pH fluctuations and adsorptive capacity of the composite media, achieving 40–70% reductions overall. Microbial analyses revealed robust denitrification activity consistent with warm temperatures, though nitrification was sensitive to episodic low-oxygen events during peak inflows. Plant species with deep root systems demonstrated greater pollutant uptake and root-zone stabilization, while media aging reduced infiltration rates, necessitating periodic rejuvenation. Economic assessment highlighted life-cycle costs, operation and maintenance requirements, and carbon sequestration benefits relative to conventional drainage approaches. Scenario analyses demonstrated that the system’s performance is resilient to forecasted climate variability, though design adaptations (e.g., embedded wetlands, increased storage volume) improved flood attenuation without compromising pollutant removal. The study provides actionable guidelines for community-scale implementation in tropical cities, including recommended media compositions, planting schemes, maintenance regimes, and monitoring protocols. It also identifies knowledge gaps related to long-term media degradation, microplastic fate, and synergy with urban green infrastructure networks, offering a framework for scalable replication and policy integration to advance sustainable stormwater governance in tropical urban environments. The findings contribute to a robust evidence base for optimizing bioretention design under tropical climate constraints, balancing hydrological safety, water quality gains, and community co-benefits.

Project Overview

What This Project Is About

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A simple study that looks at using a small, planted basin near urban streets to manage rainwater and remove pollutants. It tests how a bioretention system works in a tropical city, where heavy rainfall and heat can affect water quality and system performance.

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The Problem It Addresses

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Cities often flood during storms and release polluted runoff into rivers. Traditional drainage can fail in tropical climates due to heavy rains, warm temperatures, and high contaminants. This project explores an eco-friendly solution that treats runoff close to where it happens and reduces pollution.

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Objectives of the Project

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1. Explain how bioretention systems work in tropical weather.
2. Assess how well the system removes common urban pollutants (like nutrients, heavy metals, and sediments).
3. Monitor the system’s performance during different rain events.
4. Provide design guidelines for small communities to implement similar setups.
5. Evaluate maintenance needs and long-term viability.

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What You Will Do Step by Step

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1. Review background literature on bioretention and tropical climate effects.
2. Design a small-scale bioretention setup for a campus or neighborhood site.
3. Install or simulate the system and collect rainfall, runoff, and water quality data.
4. Analyze pollutant removal efficiency and system performance across events.
5. Interpret results and compare against conventional drainage benchmarks.
6. Develop practical maintenance and operation guidelines.

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Expected Outcome

Expected to demonstrate that a community-scale bioretention system can reduce peak runoff and remove key pollutants in a tropical setting, offering a practical design framework for local stakeholders.