Purification (or depuration) is a vital process used to ensure that shellfish consumers are protected from the risks associated with sewage-contaminated shellfish.
Purification entails placing shellfish in tanks of seawater for a minimum of 42 hours to purge any microbiological contamination they may have bio-accumulated while in the environment. Only shellfish harvested from class B harvesting areas (and where deemed necessary, class A areas) are permitted to be depurated.
Under EC Regulations EC 853/2004 (PDF, 154 KB), the approval for shellfish purification plants to operate must be given by the local enforcement authority (LEA). This is subject to the conditions set out in the Regulations and any additional conditions notified by the Food Standards Agency.
In England and Wales, Cefas has the delegated responsibility for setting the specific conditions under which the system should operate. In addition, we are UKAS-accredited against ISO 17020 for the purification system inspection service.
For new systems, "Conditions of Approval" are set following a technical inspection and, when necessary, a microbiological challenge test. Following the approval process, responsibility for ensuring that the system is maintained and operated correctly is passed to the LEA.
Operators of depuration plants who wish to obtain approval or modify a depuration plant or system should inform their local food authority. The authority will then liaise directly with us.
Specific advice about the design or running of purification systems should be sought from Seafish or another suitable consultancy.