The proliferation of microplastics (MPs) in the environment is high on the global agenda. Identifying, quantifying, and applying mitigation and remediation measures to particular sources is receiving dedicated attention from researchers, industries and policy makers. RAS systems have been queried to present accumulation of contaminants, such as heavy metals, drug residues and metabolites. Since RAS heavily reply on plastic components, the release of plastics and associated additives should also be investigated. It is essential to inventory sources to determine the potential for RAS systems to up concentrate these pollutants. We hypothesised that RAS systems will have several potential sources of plastics and associated additives, such as water treatment (particle filtration), bioreactors, and other plastic installations. The efficiency of water treatment and filtration systems are likely to remove microplastics in the form of sludge. Thus, not compromising the production of commercial fisheries products. There may also be differences between the different bed types within a RAS which could influence the dynamics and sedimentation of microplastics. Therefore, we aimed to first determine the sources, and then quantify the MPs and additives. For this purpose, we used a robust methodological approach to fill the research gaps connected to MPs pollution in RAS and farmed salmon.
Plastic material was collected from three RAS and their infrastructure. All plastic sources were analysed to identify their polymer and additive contents and a reference library created. This was used for targeted analysis when investigating the presence of microplastics within RAS facilities, specifically looking at intake water, recirculating water, sludge, fish, and fish feed. Analysis of these samples showed low levels but identified several potential sources of microplastics, including plastic infrastructure and consumables. Potential sources originating from the RAS infrastructure were identified as the fix bed bioreactor (FBBR) and moving bed bioreactor (MBBR), and biomedia. Screening for additives identified that several plastic-related chemicals were ubiquitous in RAS recirculating waters, including selected antioxidants and plasticisers. The source and distribution of these chemicals was compound specific. Fewer chemicals were quantified in sludge and fish compared with water. But specific compounds including antioxidants and plasticisers were consistently found in fish.