Enhanced Aerobic bio-remediation of Chlorinated Solvents at a strip mall in York, PA
Enhanced Aerobic Bio-remediation Report
Introduction
In this report, we present data collected on aerobic bio-remediation of soil contaminated with Perchloroethene (PCE), Trichloroethene (TCE), cis-1,2-Dichloroethene (cis12DCE) and Vinyl Chloride (VC) using VaporRemed.
Enhanced Aerobic Bio-remediation of Chlorintaed Hydrocarbons
In Situ Bioremediaton : When Does It Work?, lists at least three criteria for demonstrating that in situ bio-remediation is effective for a given site:
- Documented loss of contaminants from the site due to bio-remediation,
- Laboratory assays showing that the micro-organisms in site samples have the potential to transform contaminants under expected site condition, and
- One or more pieces of evidence showing that the bio-remediation potential is actually realized in the field.
The following gallery shows presents the data collected over a two year period, between May 2017 - Mar 2020.
Summary of data for indoor air in one of the hotspots.
We had identified 12 rooms for monitoring levels of TCE and PCE; of these rooms, the room closest to the sub-slab area IA-001 was monitored more actively. The graph below shows contamination levels of TCE, PCE, 1,2 cisDCE and VinylChloride between 2018 - 2020.
TCE reduction in indoor air between 2018 - 2020
- June 2018 - 97.8 ppb
- July 2019 - 26.8 ppb
- Mar 2020 - 3.4 ppb
PCE reduction in indoor air between 2018 - 2020
Similar numbers can be seen for PCE, as seen below: - June 2018 - 719 ppb - September 2019 - 1050 ppb - September 2019 (next day) - 939 ppb - Mar 2020 - 186 ppb
The indoor air values for PCE levels reduced by 10.5% within 24 hours to convince us of the impact of adding VaporRemed in the subslab area. We will be continuing this theme in the rest of the post.
VC reduction
After April 2019, the levels of VinylChloride reached non-detect. More about this later.
Summary of data for Near Source Soil Gas Data.
Soil gas data that we recorded after adding VaporRemed in the second week of December 2019 shows a significant reduction of PCE within 10 days time. The straight line slope on a log scale indicates an exponential decay. The slope is quite steep and the two points that we would like to focus on are
- December 4th - 1, 570,000.00 ppb
- December 12th - 80,400.00 ppb.
Assuming an approximate first-order decay of PCE and TCE were computed as follows:
- PCE - -37%
- TCE - -19%
The difference in rates of PCE and TCE is important as we noticed that the levels of TCE rose before they actually fell down, indicating that the PCE was being broken down to TCE and was being added to the available TCE in the system that was being bio-remediated.
Summary of data in Soil.
In the report we observe increase levels in Vinyl Chloride indicating active bio-remediation by VaporRemed.
First-order decay formula used in this report
Definition : A quantity is subject to exponential decay if it de- creases at a rate proportional to its current value. In this report and the attached source code, we are using the following formula:
rate = oneDay ∗ (ln r2 − ln r1)/timeInSeconds. Where
oneDay = 24 ∗ 3600 seconds
where timeInSeconds is difference in time in seconds r1 is the contamination level at time T1 r2 is the contamination level at time T2.
Summary
What we have noticed during the entire project is that VaporRemed quickly reduces contamination levels in any of the media that we have tested so far:
- Soil
- Near source soil gas
- Indoor air
Further, VaporRemed is not a masking agent, therefore the remediation can be attributed to the action of VaporRemed on the contaminants.