Biological activated carbons and graphenes for nitrogen removal

Overview

This research addresses the challenge of removing organic nitrogen from stormwater using biological activated carbon (BAC) and graphene-based adsorbents. Organic nitrogen can be assimilated by heterotrophic bacteria that colonize the surface of activated carbon, enabling biological nitrogen removal. However, the pore structure of conventional activated carbons can limit biofilm development and reduce adsorbent performance. Graphene sheets offer a unique alternative due to their open, sheet-like structure, which can accommodate both contaminants and microbial communities more effectively than traditional porous carbons.

The solution targets practical challenges in stormwater treatment, where variable water quality and competing dissolved organics often limit the performance of conventional adsorbents. The research also explores coupling these biological adsorbents with pre-ozonation to convert organic nitrogen species into ammonia, enabling deeper nitrogen concentration reductions in future applications.

Technical specifications

• Adsorbent comparison: Systematic investigation of enriched microbial consortia on graphene sheets versus multiple commercially available activated carbons
• Graphene advantage: Open sheet-like structure mitigates pore blocking and accommodates microbial communities alongside contaminant adsorption
• Hybrid treatment concept: Biological graphene adsorbents coupled with pre-ozonation to convert organic nitrogen into ammonia for enhanced removal
• Microbial enrichment: Development of enriched heterotrophic bacterial communities native to secondary wastewater treatment, fed ammonia in flow-through reactors
• Testing approach: Batch tests across various water matrices to identify optimal operational conditions, combined with rapid small-scale column tests (RSSCT) using actual stormwater runoff from different rain events
• Analytical capability: Time-course quantification of nitrogen species throughout the hybrid biological/physical treatment process

Technology readiness level

The research team has over a decade of experience in passive treatment technologies and adsorption of pollutants by novel carbon adsorbents compared to commercial activated carbons. Current efforts focus on demonstrating the utility of graphene's sheet-like structure and suppression of pore-blocking mechanisms. Future validation will involve creating enriched microbial communities on adsorbents in flow-through reactors and testing them in batch and column-scale experiments using real stormwater matrices. The technology is in the research and validation phase, with ongoing development toward identifying the best operational conditions and adsorbent configurations for practical deployment.