Remediation and valorization of process streams in ragworm culture
In the Province of Zeeland ragworms (Nereis virens) are farmed on large scale (6 ha) in open rectangular (flow through systems) ponds. In April the ponds are stocked with ragworm larvae, from the hatchery. From a certain size/ age on the juveniles burry themselves in the sediment layer in the pond and are fed with feed pellets. Depended on the market (bait for fishing or maturation feed for shrimp farming) the market size ragworms are harvested after 7 – 20 months.
Ragworms are in principle omnivorous animals, but can also perform filter feeder characteristics. In the ponds with ragworms occasionally a significant microalgae production occurs. Experiences with combining ragworms and bivalve shell fish are promising: Both type of animals showed a significant growth. Separate production, in different systems, of ragworms, microalgae and shellfish is however, preferable. It seems as if there is a huge potential to grow microalgae and subsequently bivalve on the process stream of ragworms ponds. However, little is known about the composition in terms of dissolved nutrients and particles of the waste streams, under different conditions (density of ragworms, seasonal variations, amount and type of feeding, etc.).
To investigate the potential of process streams from ragworm farming, knowledge is needed about mass balances of ragworms farmed in ponds fed with pellets. Knowledge questions focus on: What determines the composition and total amount of the process streams in ragworm farming? How can the process streams being used in an optimal way, in terms for algae and shellfish production facilities?