Bioremediation of Polychlorinated Biphenyls (PCBs)


Technology: The invention includes compositions and methods for bioremediation of PCBs using anaerobic microorganisms that remove chlorines from PCBs and aerobic microorganisms that then break down the remaining biphenyl rings. The PCB-degrading microorganisms are inoculated onto pellets called SediMite™ that contain activated carbon, sand and binder. SediMite™, developed by Sediment Solutions, is dispersed into sediments using a venturi air mover or telescopic belt conveyor. The pellets, saturated with PCB degrading microorganisms, sink to the bottom of the waterways and dissociate in the contaminated sediment. Bottom-dwelling organisms such as worms then work the microorganisms deeper into the PCB contaminated sediment as a result of burrowing activities. PCBs are rapidly absorbed by the activated carbon effectively sequestering them from the food chain and the PCB degrading microorganisms then degrade the absorbed PCBs. This treatment reduces PCB accumulation in aquatic animals with the end result of lifting fish advisories in impacted water bodies. Lab sediment mesocosm treatments consistently achieve 75-80% reduction in PCBs levels within one year, whereas untreated sediments show no change.


A pilot test to determine the efficacy of bioaugmentation in the field was initiated in 2012 at an emergency overflow pond containing Aroclor 1242/1248 at concentrations up to 2400 mg/kg. Initial in situ tests in 2.8 sq. ft. caissons achieved 80% reduction in PCBs in the top 6 inches after 990 days, meeting the target level of 50 PPM. No change was observed in untreated sediment. Based on these results a Phase II pilot test was begun in 2015 using 80 sq. ft. caissons. Initial results already show 21% reduction of PCB levels only 90 days after treatment. Sampling will continue into 2017. Another 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 already achieved 53% reduction in PCB levels in the benthic zone after 13 months. No changed was observed in untreated sediment plots. Sampling will continue into 2016.


Overview: National fish advisories are currently in effect for 1,040 waterbodies in the U.S1. Twenty three percent of all advisories in effect are due to PCBs. This represents 6 million lake acres and 132 million river miles of PCB-contaminated sediments. In Maryland alone there are consumption advisories due to PCBs in 20 aquatic species residing in over 50 water bodies. Currently less than 1% of PCB-impacted sites have undergone treatment in part due to the high cost of the current technologies available, dredging and capping. Dredging a 40-mile stretch of PCB contaminated sediments in the Hudson River alone cost $1.6 billion. The potential market for more cost effective technologies for treating rivers alone in the U.S is over $5 billion.


Current technologies, dredging and capping, are expensive, destructive to environmentally sensitive areas and may not sufficiently reduce the risk because of limitations inherent in the technologies. Development of a tractable microbial in situ treatment system would revolutionize the field by providing the most practical, cost-effective, and environmentally sustainable means of treating persistent pollutants. The technology is expected to cost approximately $150,000 per acre, which compares favorably with the current technologies.


In addition to lower cost, the addition of activated carbon associated with the microoganisms immediately sequesters the PCBs from the food chain as the bioamendment degrades the PCBs over a period of months effectively reducing the health risks immediately after application. No other technology currently available is suitable for degradation of PCBs in environmentally sensitive environments.


Applications: Bioremediation of PCBs


Advantages: More cost-effective than dredging and capping; Both sequesters PCBs from the food chain and degrades PCBs; Rapidly deployed to be minimally disruptive to local activities; Environmentally sustainable; Reduces health risks associated with sediment disruption; Reduces overall energy use; Negates requirement for extensive waste management; Obviates requirement for substantial habitat restoration


Publications: Payne RB et al. "Mesocosm Studies on the Efficacy of Bioamended Activated Carbon for Treating PCB-Impacted Sediment." Environ Sci Technol. 2017 Sep 19;51(18):10691-10699.

Key Words: Bioremediation, PCBs, dredging, capping


Inventors: Kevin Sowers, Hal May

Patent Status: US 7,462,840

MUSC-FRD Technology ID: P0242


Patent Information:
For Information, Contact:
Scott Davis
Associate Director, Licensing
MUSC Foundation for Research Development
Kevin Sowers
Harold May
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