Sustainable Solutions for Remediating PCBs
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A Sustainable, Cost Effective and Scalable Technology for In Situ Remediation of PCBs
RemBac Environmental LLC provides sustainable, environmentally friendly materials and expertise for in situ bioremediation of sediments and soils contaminated with polychlorinated biphenyls (PCBs), a global toxic pollutant. Our patented technology provides three critical advantages for site remediation: 1) the combined action of naturally occurring PCB degrading bacteria with activated carbon both degrades and sequesters PCBs to mitigate their toxicity, 2) the approach is cost effective and can be used as an alternative or in combinaiton with current technologies for PCB treatment such as dredging and capping, and; 3) it meets the growing demand for sustainable treatment alternatives with a lower carbon footprint and reduced risk to human health and the environment.
HOW BIOREMEDIATION OF PCBS WORKS
THE BIOAMENDMENT
Biological degradation of PCBs in the environment occurs by anaerobic dechlorination of highly chlorinated congeners followed by the aerobic degradation of the dechlorination products. However, a key bottleneck is the low native abundance of PCB degrading bacteria found naturally in sediments. Treatment with bioamended AC enhances the natural degradation of PCBs by increasing the numbers of PCB anaerobic dechlorinating and aerobic degrading bacteria in the contaminated sediment. The microbes are grown in high volume bioreactors, concentrated by centrifugation or filtration and shipped to the field for deployment. The bioamendments occur naturally in the environment and are non-GMO and non-pathogenic. (U.S. Patent No. 6,946,248, 7,462,480 B2)
BIOAMENDED ACTIVATED CARBON
Bioamendments can be applied to PCB impacted enrivonments by several methods. The most common method for treating sediments is to apply the bioamendments to pellets of activated carbon pellets (SediMite™) which act as a delivery system for inoculating the sediments at the site. (U.S. Patent No. 8,945,906)
APPLICATION
There are several options for deploying bioamended pellets into sediments depending on the site. These can include a ventrui horn induction system for smaller and difficult to access sites (< 1 acre), and a telebelt or barge mounted pellet broasdcaster for larger projects (> 1 acre). Bioamendments can also be applied to powdered or granular AC for direct tilling into sediment or soil. Bioamended AC can be rapidly deployed at relatively low expense and generates a minimal carbon footprint.
EFFECT OF BIOREMEDIATION ON PCBS
The highly absorptive quality of AC combined with the accelerated rate of PCB degradation by the bioamendment provides sufficient dosing with minimal material. The bioamended AC is applied to sediments forming a reactive barrier layer over the PCB contaminated sediment. In the short term the bioamended AC sequesters and degrades any PCBs that diffuse from the PCB contaminated sediment; over the longer term the bioamended AC is mixed into the contaminated sediment by natural bioturbation and remains there as a barrier that effectively inhibits movement of residual PCBs into the food chain.
SERVICES
SITE EVALUATION
RemBac will assess the PCB impacted site to determine whether bioremediation is a suitable treatment option either alone or incombination with other treatment options. We also work with the client to determine the best application method and dosage for a specific site.
APPLICATION
RemBac will provide the required dosage of microorganisms and activated carbon to treat the PCB contaminated site. We also work closely with the client and site contractor on logistics including staging, equipment requirments and application methods.
POST-TREATMENT EVALUATION
RemBac will advise clients on appropriate post-assessments required to monitor the effectiveness of the treatment and assist with interpretation of data for reports to stakeholders and regulators.
CASE STUDIES
PILOT SCALE TREATMENT OF A WETLAND DRAINAGE CREEK IN QUANTICO, VA
A pilot test was initiated in 2015 at a wetlands drainage creek containing Aroclor 1254/1260 at concentrations up to 5 mg/kg. Initial in situ treatments in 400 sq. m. plots achieved up to 52% reduction in total PCB mass and 78% reduction in porewater concentrations after 13 months. No significant changes were observed in untreated and abiotic sediment plots.
BIOREMEDIATION OF HIGH LEVELS OF PCBS IN A SLUDGE DIGESTION POND, VA
Pilot tests to determine the efficacy of bioaugmentation have been ongoing since 2012 at a 6 acre emergency overflow pond containing Aroclor 1248 at concentrations up to 2400 mg/kg. Initial in situ tests in 2.8 sq. ft. caissons showed 275 mg/kg (80%) reduction of PCBs in the top 6 inches and 569 mg/kg (42%) reduction of PCBs in the bottom 6 inches 519 days after treatment. A Phase II pilot test begun using 80 sq. ft. caissons with bioamendment mixed into top and bottom sediments with a sump pump. to ensure distribution of the bioamendment throughout the sediment column. Total PCB mass decreased by 77% (1031 to 240 mg/kg) in 50 months. Caissons not treated with bioamendment showed initial PCB degradation of 40% possibly due to aeration but further degradation was not observed after 12 months.
KURE ATOLL, HI
The goal of the treatment was to reduce potential PCB exposure from a scrap metal dump contaminated with Aroclor 1260 to marine life in the vicinity of Green Island in the Kure Atoll. Due to the very remote location of this contaminated material was transferred to a lined landfill on the island and treated by in-situ bioremediation. Total PCB mass reduced by 48% (1.8 to 0.9 mg/kg) after 32 months.
CONTAMINATED RIVER SEDIMENTS IN SOUTHEAST MICHIGAN
Aroclor 1248 was discharged in industrial wastewater into a river and nearby wetlands until the late 1970s and the site was placed on the National Priorities List (NPL; aka Superfund) in 1983. Treatability studies conducted in 2 L sediment mesocosms from two sites in the river demonstrated that treatment reduced PCB mass 78 % in 180 days. Bioaugmentation also reduced bioavailable PCB levels by 90 and 93% in sediments from the two sites tested.
A STREET CHANNEL, WILMINGTON DE
For this Delaware Department of Natural Resources & Environmental Control sponsored project a tidal wetlands channel contaminated with PCBs was treated with bioamended GAC to reduce the potential for contamination of the Christiana River. Approximately 6.5MT of bioamended SediMite was applied with a modified venturi air mover. Treatment effectiveness is being monitored in sediment cores and by passive sampling. For more info: https://www.facebook.com/rembacenvironmental/videos/477699982996365/?modal=admin_todo_tour
FORMER INDUSTRIAL COOLING POND, ANNE ARUNDEL CO., MD
Former cooling pond contaminated with a surface area approximately 22,072 ft2 and average water depth between 2 and 4 feet. Primary contaminants were PCBs composed of Aroclor 1254 and 1260 at an average concentration of 704 μg/kg. Treated with 15 MT bioamended SediMite. Total mass of PCBs decreased by 72% (703.8 to 317.6 μg/kg) and dissolved PCBs decreased by 97-99% 15 months after treatment.
SMALL BOAT HARBOR, OAHU, HI
Preliminary testing of large-scale deployment of bioamended SediMite was conducted at a marine boat harbor contaminated primarily with Aroclor 1260. 45 MT of bioamended SediMite were deployed over approximately over 1 acre. Results are pending.
EXPERTISE
Kevin R. Sowers, Ph.D., a co-founder of RemBac Environmental, has over 35 years experience in anaerobic microbiology and has expertise in the selection and scaleup of PCB dechlorinating microorganisms, and development of methods for application of microbes in the field.
Upal Ghosh, a co-founder of RemBac Environmental, has over 20 year experience in environmental engineering and science with a focus on the fate, effects, and remediation of toxic pollutants in the environment. He is also president of Sediment Solutions, LLC. which markets SediMite, a pelletized form of activated carbon.
