Effective nitrogen and phosphorous removal in recirculation aquaculture systems (NAPRAS)

Project Details


Aquaculture offers an opportunity for sustainable fish production. However, the sector is becoming restricted by water discharge quotas and must compete with traditional fisheries.

Improved effluent treatment and economies of same will allow the sector to grow. Land based Recirculating Aquaculture Systems (RAS) are being increasingly implemented in both freshwater and saltwater and with a higher degree of recirculation. High-RAS can be defined as >90% recirculation.

The Danish government has adopted policy to reduce both the discarge of N and P to aquatic ecosystems and the significant reduction of climate impact contributions from actors across the primary production sectors. A CO2 tax is currently being debated.

The NAPRAS project will develop and demonstrate a novel end-to-end effluent treatment process for RAS aqauculture - NAPRAS - that removes >95% N, 100% of N2O and >95% P, and may allow for higher production capacity within quotas and/or reduce discharges of nutrients and emissions of greenhouse gasses as well as effluent treatment costs. The one major new process, granular sludge technology, is climate friendly, requires significantly less reactor volume and has substantially lower costs than todays activated sludge technology. The other major new process, Power-to-P electrodialysis, converts electricity and sludge into a bioavailable source of P as fertilizer while effectively removing 90% of heavy metal contaminants.

The project consists of six work packages (WP):

- WP1 Project management
- WP2 Development of granular sludge technology for N removal
- WP3 Development of P capture and heavy metal removal
- WP4 Development of dried granulated fertilizer product
- WP5 Pilot validation
- WP6 Demonstration at RAS operator and dissemination

Alumichem, Denmark (coordinator)
National Institute of Aquatic Resources (DTU Aqua), Denmark
Clean Matter Aps, Denmark
Drying Matters Aps, Denmark

Associated partner: Danish Salmon, Denmark

The project is funded by the Green Development and Demonstration Programme (GUDP) administered by the Ministry of Food, Agriculture and Fisheries of Denmark

Research area: Aquaculture
Effective start/end date01/01/202431/05/2026


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