Scaled Bioaugmentation Injection Strategy for Remediation of Mixed Chlorinated VOCs in a Fractured Shale Aquifer

Scaled bioaugmentation using an optimized strategy was applied to a mixed plume of chlorinated ethenes and methanes, primarily dissolved trichloroethene (TCE) and carbon tetrachloride (CTC), in a bedrock residual source area at the head of a 132-acre plume. We evaluated key fracture pathways, VOC degradation, bacterial census, CSIA, abiotic mechanisms, methane and ketone results to design the full-scale remedy, including addressing challenges of emerging contaminant 1,4-dioxane.

The mile-long commingled VOC plume in bedrock extends through a densely populated area located in the Newark Basin of northern New Jersey. Bioaugmentation was first applied in a 2015 pilot study primarily because of the lack of naturally-occurring bacteria in the bedrock aquifer. Three years of performance metrics showed significant mass reductions and informed the final 2019 remedial design; scaled 2019 bioaugmentation injections into eight bedrock wells, with geochemical reduction as an alternative. The injection design was optimized by modifying the volume of carbon substrate in bedrock to mitigate methane production, selecting of an alternative buffer to optimize pH, and the use of two different substrate products. We utilized geochemical conditions to degrade chlorinated solvents by biotic as well as abiotic methods (ferrous iron released from the matrix precipitated as iron sulfide).