Wastewater secondary treatment in RAS with microbial biomass output

Land based aquaculture is rapidly expanding, and Norway is a leading developer of recirculation aquaculture systems (RAS) with companies like Nofitech that produces module-based RAS. The water effluent from RAS is minimized, but rich in minerals such as nitrogen, and may lead to unwanted growth of algae or weeds if released to a recipient. Water treatment and N removal represents a cost and it is relevant to consider re-use of the N-rich effluent in production of new biomass which can be used e.g. in feed production. In WASTELESS we will perform water treatment using a novel cultivation concept where biomass is growing on a bioreactor. The biomass consortium will consist of different microorganisms such as microalgae, cyanobacteria and ciliates, and they will work together in a balanced system. Using monitoring and process control, it is possible to harvest almost all the N before the water is released or returned to the RAS. The produced biomass is rich in proteins, carbohydrates, essential oils and other valuable ingredients, which can be used in feed and substitute other non-sustainable ingredients such as soy and fish meal. All agreements have been signed and the project had its official kick-off meeting. The project consortium explored bioreactors available off the shelf, but decided to produce own bioreactor technology for the project to maintain independence and intellectual property rights. The planning of the reactors and related experimental is in progress.

Land-based aquaculture is growing, and Norway is a strong partner in development with companies like Nofitech who designs and delivers module-based Recirculating Aquaculture Systems (RAS). Although waste water is minimised in RAS, release of N-rich water to a recipient may lead to undesirable eutrophication and some countries regulate the release of N from land-based aquaculture. Water treatment before release implies a cost to the producer. At present, there is no established system for collection and reuse of RAS release water into new productions such as in aquaponics. Moreover, existing aquaponic systems have large area footprints and production is mainly developed to grow freshwater plants such as salad and herbs. The release from post-smolt RAS is saline and favours production of organisms that tolerate brackish or seawater such as seaweeds or marine microorganisms. In WASTELESS we want to introduce secondary water treatment in RAS using a novel reactor concept, the Rotating Algal Biofilm Reactor (RABR). The area footprint of the reactor treating the effluent from RAS can be minimized by increasing the height and length of the belt, and harvesting of a biofilm is energy efficient compared to harvesting by centrifugation. Efforts to grow marine biomass on waste streams using single species cultures require rigorous control. Instead, we suggest establishing multi-species biomass production and use known ecological principles to optimise nutrient removal and cleaning of the RAS water. The actors will probably be a mix of organisms (i.e. bacteria, cyanobacteria, algae and ciliates), which have valuable properties in fish feed, and we will exploit the complementarity rather than fight the complexity. Furthermore, new ingredients for aquafeed can be produced from the N-rich RAS release by biorefining the produced biomass paste into clean fractions of proteins and fatty acids for example to replace less sustainable ingredients in aquafeed such as soy or fish oil.