Study of In-Situ Treatment Using Powder Activated Carbon Demonstrates Minimal Short- and Long-Term Effects on Benthic Communities

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ESTCP Project of the Year Evaluated Benthic Community Changes in Response to the AquaBlok's AquaGate+PAC Amendment for Contaminated Sediments

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According to a recent report from the Environmental Security Technology Certification Program (ESTCP), powder activated carbon (PAC)-based materials do not have negative short- or long-term effects on benthic communities.

The ESTCP evaluated the benthic community at a site contaminated with polychlorinated biphenyls (PCBs) located at the Puget Sound Naval Shipyard & Intermediate Maintenance Facility in Bremerton, Washing. Data was collected prior to application of the PAC-based material, AquaBlok, Ltd.’s AquaGate®+PAC product, as well as 10, 20, and 30 months after. The results showed no adverse impacts to the total abundance, taxa richness, species diversity, species evenness, species dominance, and percent abundance of the five most abundant taxa in the benthic community.

In addition, sediment profile image (SPI) surveys found no difference in the percent of stations with evidence of Stage 3 taxa in the initial, 10-month, and 21-month surveys (see photo). However, the percent of stations with Stage 3 taxa within the target area were lower in the 0.5- and 33-month surveys. While the cause of the reduction at the berthing area in the 33-month survey is unknown, it is believed to be related to physical disturbances caused by ship movement at the site, as the shipyard is an active Department of Defense (DoD) harbor. Further monitoring of the site will determine if this was the case.

Despite past studies questioning the potential negative impacts of PAC on benthic communities, this report proves otherwise. The product that was used, AquaGate®+PAC, is an aggregate core wrapped with PAC and a bentonite clay binder. The PAC material sorbs contaminants, like the PCBs found at the Bremerton site. This effectively reduces bioavailability and limits bioaccumulation of contaminants into the tissues of benthic invertebrates, such as mollusks and corals, and subsequently the food web.

According to the ESTCP report, a similar project at Hunters Point Shipyard in San Francisco Bay resulted in an 85-90% reduction in PCB bioaccumulation in benthic invertebrates. Also mentioned in the report is the Upper Canal Creek at the Aberdeen Proving Grounds in Maryland, where three activated carbon materials, including AquaGate®+PAC, were used. In that project, PCB bioavailability was reduced and no significant phytotoxicity or impact or species abundance was shown.

For more information and to view the complete report, please visit https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Sediments/ER-201131/ER-201131

About AquaBlok
AquaBlok, Ltd. is a manufacturing company based in Swanton, Ohio. Using its patented coating and amendment technology, AquaBlok produces low permeability and treatment materials for a range of geotechnical applications and contaminated sediment remediation projects. Product descriptions and case studies can be found at http://www.aquablok.com.

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Katie Chantler
AquaBlok, Ltd.
+1 (419) 825-1325
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