Theme: 04. Addressing Challenging Site Conditions

Topic Area: 4d. Large, Dilute and Commingled Plume Case Studies

Formatted Title:

Lessons Learned from Large-Scale Bioaugmentation at a Remote Site

Background/Objectives:

Background/Objectives. Industrial activities at a former manufacturing facility resulted in trichloroethene (TCE) impacts to soil and groundwater, and enhanced reductive dechlorination (ERD) was the selected remedy. Bioaugmentation was included in the remedial design and based on the plume size and project schedule a total of 1,893 liters of Dehalococcoides (DHC) was applied across two plumes over 3.5 acres in a period of less than three weeks. This volume of DHC is one of the largest injected in such a short period of time that has been reported by SiREM. Additional challenges associated with the site included forested and sloping topography, the need for significant clearing, biological hazards, and the potential of unexploded ordnance.

Approach/Activities:

Approach/Activities. Implementing the large ERD and bioaugmentation required significant planning between the site owner, consultant, injection contractor and bioaugmentation culture vendor to coordinate culturing, invoicing and payment plan, shipping, receiving, on-site storage, and injection. Planning for on-site storage for an early spring injection needed to consider the possibility of both freezing and warm temperatures for the site located in the southeast region of the United States. Initial discussions began six months prior to mobilization. Bioaugmentation culture production needed to be scaled up to accommodate this order in addition to other customer orders. Receiving needed to take into account that the site did not have a formal address, and the nearest street address is in a different state. The design application volume exceeded practical shipping volumes therefore culture was prepared as 189.3 L of 10X concentrated culture shipped in five 20 L vessels and a 100 L vessel. Due to the large culture volume and absence of infrastructure at the Site, a third party was identified to receive the DHC kegs into a climate controlled (not refrigerated) storage area and transportation from the third-party location was coordinated by the injection contractor. Bulk quantities of anaerobic water were prepared and used to protect the bioaugmentation culture during injections into the subsurface. Deoxygenated water and electron donor solution were prepared simultaneously and applied as a protective “sandwich” surrounding each dose of anaerobic microbial culture injected.

Results/Lessons Learned:

Results/Lessons Learned. Bioaugmentation using DHC has been used for nearly two decades to support and accelerate site remediation. This project represented an especially aggressive bioremediation approach with respect to bioaugmentation dosage and project injection schedule. Pre-injection TCE concentrations ranged from 2,000 to 20,000 ppb. Post-injection TCE concentrations have been reduced to non-detect in all target treatment areas. Conversion to cis-1,2-dichloroethene and vinyl chloride was observed following the initial injection event; however, detected concentrations of cis-1,2-dichloroethene and vinyl chloride are trending downward after 10 months of monitoring. DHC concentrations were also monitored from down gradient monitoring wells as another line of evidence for successful bioaugmentation. Due to inflation and volatility of raw materials used in carbon substrate electron donors, modifications to the ERD design were made to the follow-up injection event. This presentation will summarize the numerous challenges to performing a large bioaugmentation program, highlight the results to date and discuss how planning allowed the event to be conducted safely and successfully to aid other practitioners undertaking large bioaugmentation projects in the future.

Paul Dombrowski

Affiliation

Biography

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