The length of the period of purification should be adapted to the water temperature and physical water quality parameters (clean sea water, salinity, dissolved oxygen and pH levels suitable to permit the bivalve molluscs to function normally), the degree of contamination before purification and the bivalve molluscs species. Microbiological investigation of process water and of bivalve molluscs meat should be used to assess purification parameters. It should be taken into account that viruses and Vibrio