Primary Author/Conference Presenter:
Kent Armstrong
TerraStryke Products, LLC
Andover, NH, USA

Richard Schaffner, Jr., CGWP-Schaffner Applied Biogeosciences, LLC, Williston, VT, USA

Proof-of-Concept study evaluating efficacy of biostimulation additive TPHenhanced™ to 1) enhance respiration of indigenous heterotrophic bacteria; 2) expedite solubilization of residual source mass (LNAPL), and 3) enhanced destruction of dissolved-phase petroleum hydrocarbons (PHC) under anaerobic conditions. Site an abandoned upstream oil-gas facility. Saturated-soils/groundwater proximate to production-water retention pond adversely impacted by PHCs; specifically, Benzene above Colorado regulatory standards.
Baseline [BTEX] ranged sitewide from 2.4 mg/L to 10.6 mg/L. March 2017 impacted saturated-soils amended using one passive release sock (PRS) deployment unit (2lbs additive) in each of 26 deployment-nodes previously installed during unsuccessful ISCO events. Each node extends ≈10ft bgs with bottom 5-feet screened within saturated soil column. PRS units create ≈3-5-foot AOI. April 2017 second deployment event occurred. Two monitoring locations were evaluated: one within (MW-07) the amending zone, a second (MW-04) downgradient the amending zone. Five performance monitoring/sampling events completed during 9-month evaluation.
Results: 1) with increased additive availability Oxygen Reduction Potential (ORP) values increase; 2) enhanced reductions in dissolved-phase PHC contaminants observed under anaerobic conditions; 3) expedited solubilization of residual source mass realized, presumably due to increased viability of growing heterotrophic bacterial community. We propose, additive enhanced populations reached certain level then chemo-actively sense ‘themselves’ and, using Quorum Sensing Signaling (QSS) behavior, collectively secrete natural surfactants increasing contaminant bioavailability and microbial efficiencies associated with nutrient and food source (PHC) utilization maximizing PHC degradation rates.
Observations: with increased additive loading dissolved-phase [BTEX] decreased 84% (MW-04) and 79% (MW-07) demonstrating enhanced microbial activity. We propose, as microbial populations grew, QSS behavior resulted in expedited solubilization of residual mass, seen as 500%-1,000% increase in [BTEX] following initial decreases. At peak solubilization, rapid additive utilization is observed followed by dramatic decreases in dissolved-phase [BTEX]. Specifically, from peak bioavailability [Benzene] decreased 98.4%, [Ethyl Benzene] 83% and [Xylenes] 97.4% at MW-04.
We propose additive enhanced bacterial populations utilized the additive as alternative electron acceptor and dissolved-phase [BTEX] as electron donor, i.e. an energy-carbon source providing cellular building block-materials to grow the PHC degrading ‘community’. PHC degradation continued as additive availability was exhausted suggesting the duality of the additive; a Nitrate component to enhance native heterotrophic microbial respiration and in turn PHC destruction; and a proprietary macro-micro nutrient formulation, to stimulate the syntrophic relationship between methanogens and fermenters as the Nitrate is exhausted. Via endogenous decay, the microbial populations appear to naturally recycle additive supplied nutrients to maintain a robust community, and support continued PHC destruction.
TPHenhanced™ enhances the unicellular methanogens and fermenting organisms’ ability to combine metabolic capabilities and degrade substrate(s) neither could degrade alone; while, increasing contaminant bioavailability (solubilization). Many bacteria ferment many different organic compounds; however, most can’t ‘touch’ Hydrogen (H2). Many Archaea (methanogens) ferment H2 and Carbon Dioxide (CO2) but can’t ‘touch’ organic compounds. We propose TPHenhanced™ stimulates microbial respiration and increases in microbial densities, Quorum Sensing and Signaling (QSS) like behaviour, the production of microbial secreted biosurfactants and protective structures expediting LNAPL solubilization and dissolved-phase destruction, effectively eliminating rebound ‘up-front’, by enhancing the syntrophic destruction of PHCs under anaerobic conditions.