Water treatment technology for recirculating aquaculture systems to increase efficiency by reducing the negative effects of organic matter

Prosjektet har : -Demonstrert vannstrømningsmønsteret i fisketanker i LBCC-RAS for å oppnå forbedret selvrensende tidlig fjerning av partikler og gode vannkvalitetsforhold for fisken. -Vurdert fjerning av organisk materiale ved vannbehandlingslinjer med forskjellige nivåer av kompleksitet i nedskalert RAS. Prosjektet har vist at implementeringen av membranfiltrering i RAS forbedrer i stor grad vannkvaliteten. Konsentrasjonen av partikkelformet organisk materiale (POC) og partikkelformet N var omtrent ti ganger høyere i RAS uten membran enn i RAS med membran. Konsentrasjonen av oppløst organisk karbon (DOC) var høyere i systemet uten membran, men noe høyere enn hva som forventes å se i en konvensjonell RAS. -Fant at vesentlige mekanismer som kontrollerer produksjon av avsmak i RAS, ser ut til å være optimale biofilterfunksjoner, mens fjerning av partikler fra vannet virker mindre viktig. -Karakterisert konsekvensene av forskjellige nivåer for fjerning av organisk materiale (høy og konvensjonell) i LBCC-RAS på: (1) konvensjonelle vannkvalitetsparametere, (2) heterotrof mikrobiell bæreevne, bakteriell stabilitet og nitrifiseringseffektivitet, (3) de biologiske prosessene som forårsaker avsmaksproduksjon, og (4) oppløst CO2. -En ny sensor for oppløst CO2 ble utviklet og validert i bakteriekulturer og fisketanker, kalibrert mot kommersielle sensorer og kjemiske metoder. Sensoren vil bidra til bedre kunnskap om oppløst CO2-dynamikk i RAS-systemer.

-Design and set-up of a membrane based RAS system for a better removal of organic matter: the removal of organic matter is improved by the implementation of membrane and may result in better fish growth. Though, further investigations need to be carried out to confirm these findings. -Minimizing the risk of off-flavour production in commercial fish farms : The project had identified hot-spots for production of off-flavours. With this knowledge, off-flavours can be reduced for the benefit of both producers and consumers. -A new approach for fast and accurate determination of off-flavour in water and fish were developed and optimized: Analysis of fish from various aquaculture facilities demonstrated that palatability of fish can be determined with high accuracy . -New dCO2 sensing system:A new optical sensor for dissolved CO2 was calibrated against a commercial sensor and reference chemical methods, and validated in bacterial culture and fish tank monitoring.

This project aims to develop strategies and water treatment technology for removal of particulate organic matter (POM) in land based closed containment recirculation systems for aquaculture (LBCC-RAS). This will increase efficiency by reducing waste products, off-flavour compounds and carrying capacity of bacteria. Removal of POM is the key to improve the production and product quality of fish produced in LBCC-RAS. Organic matter is the determining factor of the amount of heterotrophic bacteria that can be sustained in the LBCC-RAS. Nitrification efficiency of the bio filter is affected by the competition for space and oxygen with heterotrophic bacteria. In addition, high amounts of organic matter reduces the efficiency of both UV and ozone disinfection. Heterotrophic bacterial degradation affect the consumption of O2 ,the production of CO2 and ammonia, contribute to water colour and bacteria producing off-flavour compounds, eventually reducing the value of fish and caviar. The effects of high, intermediate and low removal efficiency of organic matter on the effects on dCO2, bacteria and off-flavour prevalence will be investigated. Both tank dynamics and water treatment in the RAS loop will be used to obtain high removal efficiency. Multiple drains with optimized geometry and hydraulics will be designed for early particles collection and to be used as a strategy in combination with techniques such as advanced membrane filtration. The effectiveness of a membrane is dependent on several ambient conditions and fouling is a challenge for membrane performance. We will aim to adapt the membrane technology, optimize the operation and maintenance in a LBCC-RAS. A close collaboration with fish-producing companies safeguard that the project is applicable for commercial aquaculture.