Biopolymer filter pads for nitrogen removal from urban stormwater runoff
A blend of biodegradable polymers (PHA and PBSA) spun into filter pads or mesh designed to remove nitrate from urban stormwater. Laboratory tests show removal rates of 20–25 µg NO3-N per gram of polymer blend per day, with potential to also reduce phosphorus. The technology offers a sustainable, deployable filtration approach for non-point source pollution control.
Overview
Urban stormwater runoff carries nitrogen and phosphorus pollutants that are difficult to remove using conventional treatment systems. Nitrate, the most challenging non-point source pollutant, does not easily bind to natural materials and often passes through stormwater infrastructure unchanged. This solution addresses that gap by using biodegradable polymer blends to create filter pads and mesh that actively remove nitrogen from runoff.
The approach combines two biopolymers—polyhydroxyalkanoate (PHA) and polybutylene succinate adipate (PBSA)—that can be extruded and heat-spun into functional filtration media. These pads can be packed into PVC pipes and deployed in field settings to treat urban runoff at controlled flow rates. Beyond nitrogen removal, the blends also show promise for phosphorus reduction, offering a multi-pollutant filtration capability.
Technical specifications
Material composition:
- Blend of PHA and PBSA biopolymers in varying ratios
- Extrudable into fibers and heat-spun into matting
- Can be formed into filter pads or mesh configurations
Performance characteristics:
- Laboratory-observed nitrate removal rates of 20–25 µg NO3-N per gram of polymer blend per day
- Removal mechanism believed to be denitrification
- Additional phosphorus removal observed, though permanence under investigation
Deployment configuration:
- Filter pads or mesh packed into PVC pipes of varying experimental lengths
- Designed for urban runoff treatment at flow rates of 1–2 gpm per square foot of cross-sectional treatment area
- Monitoring of nitrate, nitrite, ammonium, phosphate, and total suspended solids (TSS) at inlet and outlet points
Technology readiness level
The technology is currently at an early-to-mid stage of development. Laboratory testing has confirmed nitrate removal capacity and demonstrated that the polymer blends can be extruded and spun into usable filtration media. Field validation is the next step, with plans to deploy filter pads in PVC pipe configurations using campus-generated urban runoff. The research team aims to identify optimal pipe lengths and polymer blend ratios that achieve at least 50% nitrogen removal, and to determine whether phosphorus removal is permanent or transient.
About College of William & Mary
William & Mary is a public research university in Williamsburg, Virginia that combines a liberal-arts learning environment with doctoral-level research and specialized graduate programs. Its Virginia Institute of Marine Science provides co-located coastal laboratories and research vessels, enabling industry collaborations that translate field insight into deployable solutions. The university’s location in the Hampton Roads corridor places partners near NASA Langley, Jefferson Lab, and major maritime and defense assets, facilitating access to federal facilities and talent. Faculty attract competitive federal support from agencies such as NSF, NIH, DoD, DOE, and NOAA. A dedicated technology transfer office streamlines IP protection, licensing, and startup formation, with centralized support for sponsored research agreements.
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