Report Task 2.3: Particulate waste and turbidity in (marine) RAS

Particulate waste management and removal is one of the most problematic parts of recirculation aquaculture systems (RAS). Particulate waste and thereby turbidity originates from three major sources: fish (faeces), feed and biofilm (heterotrophic bacteria and fungi). Based on size and density there are roughly four categories of particulate waste: settable, suspended, floatable and fine or dissolved solids. Specific problems related to high turbidity are a decreasing feed intake by fish, causing lower growth and increasing feed loss; an increasing risk regarding pathogens increasing disease problems and gill irritation; a higher oxygen consumption of the system and more complicate visual observation of fish, which is a necessity for good farm management. Good particulate matter and turbidity control is one of the key factors determining the success of RAS. The goal of this task is to get a better understanding of the nature of turbidity and the role of the different water treatment units within RAS and finally find ways to achieve a better control of turbidity.