WP 3: Abiotic end-of-pipe nutrient removal


In work package 3 of BONUS CLEANAQ three abiotic end-of-pipe treatment technologies, phosphorous flocculation, precipitation and electrochemical nitrate removal will be investigated at experimental scale. 

There are two challenges in phosphorous discharge control currently unsolved for recirculating aquaculture systems in the Baltic Sea region. Firstly, there is very limited knowledge, and no procedure and system design for effective, simultaneous nitrogen and P removal in brackish/marine water. Secondly, state-of-art phosphorous flocculants contain polyacrylamide and due to possible environmental problems associated with polyacrylamide, sludge disposal for agriculture is hindered.

Based on the studies within this work package, recommendations for both designing new treatment systems and operating existing ones will be given for recirculation aquaculture systems in the Baltic Sea region.


  • Investigate and optimize phosphorus removal from sludge hydrolysed for nitrogen removal processes.
  • Investigate natural polysaccharide flocculants in the P removal of sludge from brackish water recirculation aquaculture systems, as means to also aid in single-sludge denitrification.
  • Investigate phosphorous precipitation by reactive column filter.
  • Investigate and demonstrate electrochemical removal of dissolved nitrogen from aquaculture effluents.
  • Investigate electrochemical disinfection efficacy on effluent from recirculating aquaculture systems.


  • Benchmark phosphorous removal by conventional flocculants without denitrification.
  • Jar tests combining organic flocculants with denitrification.
  • Studies of recirculating aquaculture systems combining organic flocculants with denitrification.
  • Reactive column filter for phosphorous removal.
  • Nitrogen removal by electrochemical technology.
  • Effluent disinfection by electrochemical technology.


  • Natural Resources Institute Finland
  • DTU Aqua, Denmark
  • Kungliga Tekniska Högskolan, Sweden
  • University of Jyväskylä, Finland




WP3 lead

Natural Resources Institute Finland


Senior Research Scientist Jouni Vielma

17 JANUARY 2022