Analysis of swale factors implicated in pollutant removal efficiency using a swale database

Area of Science:

• Environmental Engineering
• Water Quality Management
• Urban Hydrology

Background:

• Swales are traditional open-drainage systems for stormwater pollutant removal.
• Factors influencing swale pollutant removal efficiency remain poorly understood.
• Existing research lacks a comprehensive analysis of swale performance parameters.

Purpose of the Study:

• To characterize swale performance in pollutant removal.
• To identify key parameters influencing the efficiency of swales.
• To establish correlations between swale design and pollutant removal.

Main Methods:

• Compiled a database of performance results and design characteristics from 59 literature-reported swales.
• Investigated correlations among pollutant efficiency ratios (ERs) for various contaminants.
• Analyzed the influence of inflow concentration and hydraulic residence time on ERs.

Main Results:

• High ERs observed for total suspended solids (TSS) and total trace metals (median ERs ≥ 56%).
• Medium to high ERs for dissolved trace metals (median ERs ≥ 44%), with lower ERs for nutrient species (median ERs ≤ 30%).
• Inflow concentration and increased hydraulic residence time were identified as key factors influencing ERs.

Conclusions:

• Swales are effective in removing particulate pollutants through sedimentation and filtration.
• Swale design optimization, considering hydraulic residence time, can enhance pollutant removal.
• The developed database aids in understanding swale systems and improving their design for better water quality.