Green permeable reactive concrete using recycled oyster shells for stormwater nutrient removal

Overview

This research proposes a novel Green Permeable Reactive Concrete (GPRC-Oyster) that incorporates recycled oyster shells as a partial replacement for fine aggregates. The solution addresses two environmental challenges simultaneously: reducing the growing demand for raw materials such as limestone, sand, and stone used in traditional Permeable Reactive Concrete (PRC), and finding beneficial reuse pathways for waste oyster shells. The technology targets removal of nitrogen and phosphorus from stormwater runoff, which are major contributors to water pollution and eutrophication in waterways.

By leveraging the calcium carbonate content naturally present in oyster shells—similar to calcium dust used in Portland cement—the approach produces concrete with targeted strength and porosity while delivering nutrient adsorption capabilities. This dual-benefit innovation offers municipalities, developers, and environmental engineers a sustainable stormwater treatment material that supports circular economy principles.

Technical specifications

Key features:

• Sustainable material composition: Oyster shell ash replaces fine aggregates in concrete, reducing dependence on virgin raw materials and diverting shellfish waste from landfills
• Dual nutrient removal capability: Designed to adsorb and remove both nitrogen (N) and phosphorus (P) from stormwater
• Structural performance: Maintains targeted concrete strength and porosity for permeable pavement applications
• Adsorbent properties: Crushed oyster shells function as filter media and adsorbents, building on demonstrated capacity to remove up to 80% of nitrate nitrogen in prior bench-scale column experiments
• Calcium carbonate utilization: Leverages natural CaCO₃ content in oyster shells as a functional component analogous to cement-grade calcium dust

Validation approach:

• Bench-scale jar testing with varying N and P concentrations representative of stormwater over 72-hour contact periods
• Batch reactor experiments using 750 mL nutrient solutions with continuous stirring
• Long-term column studies at flow rates of 1–2 gallons per minute for 90 days with the optimized mixture
• Effluent monitoring every 48 hours to quantify sustained nutrient removal performance

Technology readiness level

This technology is currently at TRL 3 (analytical and experimental proof-of-concept). The research team has established the scientific basis through literature evidence, including prior demonstrations of oyster shell media removing 80% of nitrate nitrogen from synthetic wastewater in bench column experiments. The proposed work will generate critical data on optimal oyster shell ash proportions, concrete strength and durability impacts, and nutrient removal efficiency under controlled conditions. Successful completion of the bench-scale and column studies will establish the foundation for a Phase II project focused on field-scale nutrient removal applications.