Multiple Pathways to Bacterial Load Reduction by Stormwater Best Management Practices: Trade-Offs in Performance,...

Area of Science:

• Environmental Engineering
• Water Quality Management
• Urban Hydrology

Background:

• Stormwater best management practices (BMPs) are crucial for mitigating microbial pollution in urban runoff.
• Existing BMPs show variable removal efficiencies for fecal indicator bacteria (FIB).
• Enhanced BMPs, including media amendments, can substantially increase FIB removal, but their watershed-scale impact remains unclear.

Purpose of the Study:

• To computationally model watershed-scale bacteria loading and BMP performance.
• To evaluate the implications of varying BMP performance, treatment area, volume, and infiltrative capabilities on FIB reduction.
• To analyze trade-offs in BMP implementation for effective watershed management.

Main Methods:

• Development of a computational model to simulate watershed-scale bacteria loading.
• Case study application using the Ballona Creek Watershed in Los Angeles County, California.
• Simulation of over 1400 scenarios with diverse BMP parameters (performance, area treated, volume, infiltration).

Main Results:

• An incremental 0.25-log10 improvement in BMP performance can reduce annual bacterial load by 0-29%.
• Equivalent FIB load reductions can be achieved through different combinations of watershed area treated and BMP infiltration capacity.
• Infiltrating BMPs demonstrate superior watershed-scale FIB reduction compared to non-infiltrating BMPs.

Conclusions:

• Watershed-scale modeling provides critical insights into the effectiveness of stormwater BMPs.
• Strategic implementation considering BMP performance, treatment volume, and distribution is key for maximizing microbial load reduction.
• Infiltrative BMPs offer a promising approach for enhanced watershed-scale control of fecal indicator bacteria.