Bivalve shellfish purification | Seafish

Bivalve shellfish purification

Guidance on building and operating shellfish purification systems. The Seafish designs are frequently used by industry and are a proven technology.



The classification of a shellfish production area determines the treatment required before Live Bivalve Molluscs (often referred to as 'LBMs') may be sold for food. Our Classification of bivalve harvesting and production areas guidance provides further details. Also visit the Aquaculture water quality and classification for shellfish page for details on how we’re working with aquaculture producers, regulators and researchers looking at UK water quality to increase production of high quality shellfish.

Bivalve shellfish purification (also known as ‘depuration’) relates to the use of a controlled, aquatic environment to reduce low-level contamination by bacteria in live bivalves to a safe, acceptable level for people to eat. Purification is a natural biological process whereby bivalve shellfish purge themselves by filtering sterilised seawater.

Building a Purification Centre – Key Stages and Considerations

A purification centre has tanks fed by clean seawater in which live bivalve molluscs are placed to reduce contamination and to make them fit for human consumption. 

The following guidance document is intended to provide concise and practical advice in relation to constructing a shellfish purification centre. It offers details on four key project stages, namely, planning, site selection and permissions, design and build, and approval. It also touches on relevant training.

Bivalve Purification Systems: Operating Manuals

Whilst a shellfish business or operator can develop their own systems for purifying bivalves, Seafish has guidance on developing and operating five standard designs for bivalve shellfish purification systems, with additional guidance for developing and operating non-standard systems.

Originally developed in the 1990's, and reviewed in 2018, the six operating manuals offer technical and legal information to reflect current best practice. The standard system models described in our manuals have been extensively tested, are frequently used by industry, and are a proven technology.

Please Note: Seafish does not approve systems; this is carried out by a Local Authority.

All six system operating manuals can be accessed on the following links below. 

  • Our 'Hygiene' page looks at food hygiene legislation which affects all UK businesses involved in the handling of food.
  • Our 'Delivering Safe Bivalves to the Market' web page will further explain specific requirements to ensure bivalve molluscs are safe for us to eat by reducing the risks from microbial contamination and biotoxins.
  • Visit the Seafish 'Bivalve Purification Training' page to find out more about our approved-trainer delivered courses

The links below will take you to additional and useful bivalve purification system-related Seafish resources for you to download:

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