Biopod-hybrid adsorption biological treatment systems for stormwater

Overview

A stormwater treatment approach that enhances bioretention systems by integrating low-cost adsorptive media, such as biochar, into the bioretention media. The core concept decouples pollutant residence time from hydraulic residence time, allowing nutrients like nitrogen to be captured during storm infiltration and then biologically processed during antecedent dry periods (ADPs). This hybrid adsorption and biological treatment strategy is designed to remove total nitrogen (TN), ammonia (NH4+), and pathogens from urban stormwater runoff, addressing a major water quality challenge in growing urban areas.

Technical specifications

The system relies on the following design principles and features:

• Adsorptive media integration: Low-cost adsorbents such as biochar are blended into sand-based bioretention media to capture organic nitrogen (Org-N) and NH4+ in the upper zone during storm events.
• Dual-zone treatment profile: Biochar increases water retention without compromising permeability, maintaining high moisture content at depth to support denitrification while allowing the upper zone to drain and oxygenate during ADPs.
• Microbial regeneration: Drainage and evapotranspiration during dry periods fill rhizosphere pores with oxygen, promoting ammonification and nitrification in aerobic zones.
• Variable saturation flow modeling: HYDRUS modeling will be used to simulate infiltration and drainage cycles, guiding media composition to optimize aerobic and anoxic zone development.
• Flexible operating range: Designed to handle hydraulic loading rates of 1 to 2 gpm per square foot of treatment area and TN concentrations of 0.5 to 3 mg/L, consistent with urban stormwater variability.

Technology readiness level

Builds on prior bench and pilot studies demonstrating enhanced E. coli and TN removal in biochar-amended bioretention media. The research team has validated biochar as an effective ion exchange material for NH4+ and NO3- and has experience with slow-release electron donors to promote denitrification and variable saturation flow modeling. Future validation will include column studies to confirm adsorption behavior, HYDRUS model validation, and full-scale testing using BioPods fed with stormwater from a campus stormwater pond. The project is positioned between laboratory validation and pilot-scale demonstration, with the goal of advancing toward commercial deployment.