DE-RISKING RAS - Developing best practice for RAS bio-filters: regular 'maintenance' dosing vs. seed only dosing

The Covid pandemic has shone a light on the need for shorter food supply chains. Currently 53% of food consumed in the UK is produced here, but we are a net importer of seafood. However, with marine fish stocks currently over fished, sustainable growth in UK seafood production as a key part of any Green Recovery will have to come from aquaculture.

Recirculating Aquaculture Systems (RAS) are an on-land, tank-based aquaculture system, where water is reused having been put through water remediation systems including bio-filters.

RAS are being developed as a potential solution to the issues posed by conventional aquaculture: environmental degradation, the risk of disease or parasites (sea-lice in Atlantic Salmon, for instance), and locations far from final markets leading to high transport costs and emissions.

With closed systems and controlled conditions, RAS can solve these problems and provide a more sustainable source of seafood for UK consumers.

However, to achieve this, RAS need to overcome key challenges. Foremost among these is the risk of Hydrogen Sulphide (H2S) - a potent toxin in RAS systems. The threat of toxin spikes and so the loss of expensive stock has limited the growth of RAS; conversely, a proven method for solving this problem would help the expansion of this sustainable alternative to conventional aquaculture.

The dominant current approach by RAS operators is to 'seed' a bio-filter with bacteria when they start a system, in the expectation that the bacteria that develop with help to control toxins produced in the system, such as ammonia or nitrite. This 'seed and step back' approach can lead to sub-optimal combinations of bacteria species developing, with subsequent spikes in toxins. For instance, when sulphate reducing bacteria (e.g. _Vibrio sp._) are allowed to accumulate in the bio-filters of RAS, they will produce H2S.

This project aims to prove the validity of an innovative new approach - 'maintenance dosing'. We aim to prove that the addition of regular applications of specifically chosen bacteria to a RAS bio-filter provides the following key benefits:

* more predictable and controlled micro-biome when compared to only applying a starting application;
* prevents the proliferation of _Vibrio sp._, therefore reducing the risk of H2S;
* prevents the presence of Geosmin and MIB (common contaminants in seafood, resulting in 'off-flavour' taste).

'Maintenance dosing' is not common practice in RAS facilities either in the UK or Worldwide. Proof that this innovative approach had the material benefits outlined above would help it become 'standard practice' in the industry, and so facilitate the expansion of sustainable RAS as an alternative to conventional aquaculture.

Great British Prawns (GBP) and Nova Q have pioneered this 'maintenance dosing' approach, with successful results achieved in GBP's commercial prawn farm. However, no publicly available, replicated trials have been conducted to provide the data to support these results. This project aims to fill that gap. Great British Aquatech (GBP's R&D subsidiary) and Nova Q have partnered with Scotland's premier independent marine science organisation - the Scottish Association for Marine Science (SAMS) - to conduct this project.