Catalytic two-stage reactor for nitrogen and phosphorus removal from wastewater

Overview

This solution addresses two of the most persistent pollutants in wastewater—nitrogen and phosphorus—through a novel two-stage catalytic process. By combining an advanced electrocatalyst with a biological catalyst, the system offers a more efficient and potentially resource-recovering alternative to conventional wastewater treatment approaches.

The first stage employs a CuPd single-atom catalyst that electrochemically converts dissolved nitrates into ammonia, achieving conversion efficiencies exceeding 80% with ammonia yields up to 800 µg per milligram of catalyst. The second stage uses Trichodesmium, a bacterium that transforms dissolved phosphorus into solid phosphate, which can be easily separated from the treated water. Together, these stages offer a pathway to cleaner effluent while potentially recovering valuable nutrients.

Technical specifications

Stage 1 – Electrocatalytic nitrate reduction:

• CuPd single-atom catalyst drives the electrochemical conversion of nitrates to ammonia
• Operates in a 0.5 M sodium sulfate electrolyte
• Applied potential range of -0.9 to -1.3 V versus an Ag/AgCl reference electrode
• Conversion efficiency exceeding 80%
• Ammonia yield up to 800 µg per milligram of catalyst
• Validated in an H-cell configuration with a Nafion 117 membrane for ion exchange

Stage 2 – Biocatalytic phosphorus recovery:

• Trichodesmium bacteria convert dissolved phosphorus into solid phosphate
• Solid phosphate form enables straightforward physical separation from wastewater

Integrated reactor design:

• Two-stage flow-cell system under development to sequentially treat nitrogen and phosphorus
• Planned use of a packed-bed reactor configuration with appropriate substrate to capture usable products and discharge clean stormwater suitable for downstream treatment

Technology readiness level

The CuPd single-atom catalyst has been experimentally validated for nitrate removal, demonstrating greater than 80% conversion efficiency and ammonia yields up to 800 µg/mgcath in laboratory-scale H-cell testing. The biocatalytic phosphorus conversion using Trichodesmium is at an earlier stage, with the two-stage flow-cell integration and packed-bed reactor design planned for development with infrastructure funding. The current readiness level corresponds to early-to-mid laboratory validation, with next steps focused on scaling the system into a continuous flow-cell configuration and validating end-to-end nutrient removal and recovery.