Biochar-enhanced natural treatment systems for urban stormwater nutrient removal and reuse

Overview

Urban stormwater carries nutrients such as nitrogen and phosphorus, along with metals, that conventional green infrastructure is not designed to remove. This research advances bio-based solutions that combine natural treatment systems—constructed wetlands, retention ponds, and gravel filters—with bioresiduals-derived biochar to capture low-concentration contaminants from stormwater. The approach offers a low-cost, environmentally benign pathway for treatment and potential reuse of urban stormwater, addressing limitations of existing green infrastructure that primarily manages volume and peak flow without improving water quality.

Technical specifications

• Natural treatment systems: Constructed wetlands, retention ponds, and gravel filters capable of handling varying urban stormwater flowrates, including combined sewer overflow scenarios.
• Biochar production: Thermochemical conversion (pyrolysis) of common bioresiduals including biosolids from wastewater treatment plants, invasive wetland plants, fast-growing willow chips, and food waste.
• Biochar enhancement: Methods to increase surface area and functional groups of porous biochar through activation processes, improving adsorption capacity for nitrogen, phosphorus, and metals even at low concentrations.
• System integration: Biochar can be packed into both large-scale outdoor and small-scale indoor natural treatment systems to enhance nutrient and metal removal.
• Adsorption performance: Laboratory experiments to evaluate biochar effectiveness for adsorbing low-concentration nutrients and metals from stormwater matrices.

Technology readiness level

The underlying natural treatment systems have been validated through years of greenhouse-scale testing since 2007 and a full-scale constructed wetland for combined sewer overflow treatment. Biochar integration for nutrient adsorption is at an earlier stage, with ongoing development of production methods, activation techniques, and adsorption experiments. Future validation includes scaling biochar-enhanced systems to receive real or simulated stormwater flows and conducting preliminary economic analysis to assess commercial viability.