CLEANAQ-Innovative removal of N,P and organic matter in effluents from recirculating aquaculture systems

Purpose and goal

Innovative solutions that improve efficiency and reduce the use of external resources are important for future development of recirculating aquatic fish farming systems (RAS). Therefore, CLEANAQ aimed to develop new techniques and procedures for the brackish / saline aquaculture system in the Baltic Sea region. The general goal was to optimize RAS for denitrification and phosphorus removal. The work package in which KTH participated has had the objective to develop a filter technology to separate phosphorus. This has been met and the approach will be communicated to RAS fish farms.

Expected results and effects

Fish farming in recirculating aquaculture systems (RAS) provides possibilities for optimized food production for the benefit of the environment and farming in closed confinements. We have shown that within the recirculation loop, nutrients are mainly converted and subsequently removed from the farming system through the tested systems and that water can be recycled in a higher degree than existing systems. The use of filter media for trapping phosphorus also imply possibility to recycle P to agriculture. The results will be communicated to RAS fishfarms and producers of filters.

Planned approach and implementation

The experimental research was conducted in the laboratory (KTH) and at the fish farm Laukka, Jyväskylää, Finland. Two commercial filter materials were tested by batch and column experiments. The columns were placed on the fish farm so that effluent water could be treated in the purification system. The same water was transported to the KTH laboratory for batch experiments where the sorption capacity could be determined. All parts of the experiment imitated real operating conditions so that the results could be transmitted to large-scale use. The trials could be carried out as expected.