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Water Treatment Challenges Faced in Shellfish Purification

Bivalve mollusks (clams, mussels, oysters, scallops) collect contaminants, including viruses and bacteria, that without removal pose significant risks to humans on consumption. Purging these impurities is of paramount concern in shellfish farming and harvesting.

Bivalve mollusks are filter feeders. They gather food through their gills, taking in impurities from the water as they go.

Contaminants commonly include not only particulate matter, but bacteria and viruses that are attached to them. Risks include poor flavor to illness and even death. This creates a biosecurity issue addressed by Federal sanitary standards that shellfish farmers must meet. The nature of the contaminants determines the processing required.

VAL™ Shellfish Purification Trial: A Case Study in Pathogen & Suspended Solids Removal

U.S. oyster farmers need to comply with regulations specified in Chapter XV of the Food and Drug Administration’s Model Ordinance of the National Shellfish Sanitation Program (NSSP; US FDA 2006) detailed in the Table below, reducing adverse impact on human health.

U.S. National Shellfish Sanitation Program Shellfish Harvesting Area Classification Criteria

Total Coliforms (100 ml water)

Faecal Coliforms (100 ml water)


This trial was conducted with a VAL™600, on a tank containing 1,300 gallons of sea water and live oysters. The test results were validated by the certified AQMC laboratory (COFRAC #1-1366). 

  • Starting with an E. coli concentration 30 times the allowable coliform limit, the VAL™ reduced the coliform concentration to the 230 U/100 ml threshold in approximately 9 hours.

  • After an additional 9 hours the level had stabilized below 20 U/100 ml, less than 1/10 the allowable coliform limit.

  • This test validates the VAL™ as a highly effective tool in addressing depuration and other aquaculture biosecurity issues.

Shellfish Depuration with the VAL™

Prohibited Areas

Restricted Areas

Approved Areas

Shellfish Depuration with the VAL graph results

Download the VAL™ Shellfish Purification Case Study

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1300 gpm Oyster Depuration System

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100 gpm Oyster Depuration System

To learn more about how the VAL™ can improve performance at your shellfish operation send us an application inquiry.

Capacity: Our wide range of VAL™ models can treat 10 to 1,000 gpm of water, from purification tanks that contain 500 to 50,000 gal. of water with shellfish.

The VAL™:

  • Extracts micro-particulates and pathogens that contaminate shellfish rearing water. Micron sized air bubbles attach to surface active particles and carry them to the free surface forming a concentrated layer of foam that is then removed.

  • VAL's™ foam fractionation removes fine particles smaller than 40 µm giving rise to high quality water. The ability of VAL™ to extract microparticles makes it an effective biosecurity tool as it extracts bacteria, viruses, toxic microalgae and parasites.

  • In the process of extracting the pathogens, the VAL™ also strips carbon dioxide, reaerates and circulates the water.

Specific VAL™ Application Benefits for Shellfish Purification

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"Our new building includes 60,500 gallons of shellfish purification tanks, for a total volume of 113,150 gallons to be treated, pumped directly from the lagoon. The initial plans included the conventional sand filter pumps and UV treatment systems. Switching from these technologies to the VAL™ has enabled us to consume 8X less energy, and a higher performance in terms of water quality, both in filtration and purification as well as in oxygenation."

Guy Sanchez - G.M. Major French Oyster Producer

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Specific VAL™ Application Benefits for:

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