Mariculture technical innovations in Sweden (MARTINIS)

Purpose and goal:

The overall aim of the MARTINIS project is to combine Swedish and Japanese technologies to develop state-of-the-art marine recirculating aquaculture system (RAS).

In this experiment, we have shown that the marine strain of anammox Candidatus Scalindua could successfully be slowly adapted to RAS WW, supplemented in NH4+ and NO2-, but in the absence of TE supplementation. Future studies need to determine the specific needs for optimal RAS WW treatment by Ca. Scalindua at pilot scale.

Expected results and effects:

We have shown that during the 3 phases of the experiment, Ca. Scalindua was able to maintain relatively high & stable removal rates, both for NH4+ and NO2- (over 98%).

Despite a slight decrease in relative abundance (from 21.4% to 16.7%), Ca. Scalindua remained the dominant species in the granules during the whole experiment. The small changes observed in the bacterial communities could be due to the presence of waste and additional load of bacteria from the RAS WW, which could have led to an artefact and an apparent (slight) reduction of Ca. Scalindua in the granule.

Approach and implementation:

We have conducted the experiment at the University of Gothenburg in 2022 over 280 d. The experiment was divided in3 phases; control (0-80), adaptation to RAS WW with TE (84-200) and in the absence of TE (201-280). We have taken weekly samples of influent and effluent to measure NH4+ and NO2- in Sweden, NO3- and the bacterial community analyses were done at the University of Hiroshima (Japan), with our partner, Prof. Kindaichi.

The follow-up experiment will take place at the company Anoxkaldnes, where we will have signed an agreement to rent their facilities for 5 months, from January 2023.