Layered double hydroxide adsorbent for nutrient removal from urban stormwater runoff

Overview

Urban stormwater runoff carries excess nutrients such as phosphorus and nitrogen that degrade water quality in rivers, lakes, and reservoirs. This solution leverages Layered Double Hydroxides (LDHs), positively charged layered adsorbents with interlayer hydroxides, to selectively capture phosphate and nitrate from stormwater. A circular-economy benefit is built in: once the LDH is spent, it can be repurposed as a concrete additive that reduces chloride-induced corrosion in reinforced structures. The approach addresses two environmental challenges at once, nutrient pollution and infrastructure degradation, while creating a reusable waste stream.

Technical specifications

• Selective anion exchange: LDH interlayer hydroxides and carbonates exchange with target oxoanions (phosphate, nitrate) for high-selectivity capture.
• Multi-mechanism removal: Nutrient anions removed primarily via anion exchange; heavy metals and other species removed through precipitation.
• No pretreatment required: Operates effectively without pH adjustment or pretreatment, even in waters with high sulfate and total dissolved solids.
• High capacity retention: Only 5% of adsorption capacity was exhausted after 1000 bed volumes in prior pilot-scale column testing on powerplant blowdown water.
• Validated formats: Bench jar-tests, 0.43-inch and 2-inch diameter column tests, and a field pilot-scale study have been completed for related applications.
• Reuse pathway: Spent LDH can be incorporated into concrete to limit chloride-ion-related corrosion due to its inherent alkalinity.

Technology readiness level

The LDH adsorption platform has been validated at bench, column, and pilot scale for selenium, arsenic, phosphate, and other anions in powerplant cooling tower blowdown water. Prior work also characterized the effect of competing ions on sorption capacity. The proposed work will extend this foundation to phosphorus and nitrogen removal from actual and synthetic stormwater runoff, quantifying adsorption capacity, optimal hydraulic loading rates, empty bed contact times, and runtime-to-exhaustion through predictive mathematical models. Concrete reuse of spent LDH for corrosion mitigation will also be investigated. The technology is at an advanced validation stage and is well positioned for pilot-scale stormwater deployment and downstream concrete application studies.