Emerging Contaminants Summit

Spring 2020

mackinnonLeah MacKinnon
Principal
Geosyntec Consultants, Inc.

Ms. MacKinnon is a Principal Engineer and manager of the Remediation Group in Geosyntec’s Guelph, Canada branch. Ms. MacKinnon has over 20 years of experience in the United States, Canada, and Europe focusing on the development and implementation of effective in situ remediation and management strategies for complex sites. Her technical experience involves the fate and transport of non-aqueous phase liquids in porous and fractured media, site investigation and the design, implementation and interpretation of remediation technologies for treatment of a broad suite of contaminants including 1,4-dioxane, chlorinated solvents, perchlorate, nitroaromatics, pharmaceuticals, pesticides, metals and chlorofluorinated compounds. She is the author of numerous publications and presentations on the development and application of remedial technologies such as bioremediation, chemical oxidation, surfactants, and in situ alkaline hydrolysis.

 

PLATFORM PRESENTATION

Chemistry Rules: Developing MNA and Remedial Strategies for Norbornene Flame Retardants and Insecticides

Norbornene (or cyclodiene) insecticides (aldrin, dieldrin, chlordane, etc.) often degrade in the environment to a structurally similar compound, chlorendic acid (CA), which is recalcitrant to further degradation. This chemical is also involved in the synthesis of flame retardants, resins, coating agents, corrosion resistant plastics and lubricants. The unique chemical properties of CA make it resistant to many common in situ and ex situ remedial technologies. With a complex ring structure, six chlorines and two carboxylic acid groups, it’s behavior in groundwater can be similar to hydrophobic organic species under some geochemical conditions, and inorganic species under others.

Geosyntec has evaluated the viability of a monitored natural attenuation (MNA) remedy for a site where CA is present in groundwater. Additionally, for MNA to be accepted by the local regulators as the primary off-site remedy, a contingent remedy for active treatment in the off-site plume has been identified and designed.

To identify potential remedial technologies for CA, and to identify potential reaction processes that occur under natural attenuation conditions, a series of treatability studies has been completed. As there is limited documentation of demonstrated CA treatment processes, this has included a wide array of technologies including chemical oxidation, hydrolysis, precipitation, sorption, chemical reduction via zero valent iron, and aerobic and anaerobic bioremediation.

In parallel with this work, groundwater modeling and assessment of the geochemical conditions within the plume has been used to support the MNA evaluation. Synthesis of the model results, geochemical data, plume distribution and treatability results has confirmed that processes observed at the laboratory scale are reflected at the field scale, allowing prediction of future fate of CA at the site.

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