Description
Project: EHC Treatment of Chlorinated Solvents, Manufacturing
Facility - Belgium
Summary
A field scale pilot test was performed to evaluate the performance of
in situ biological and chemical reduction (ISCR) of chlorinated aliphatic
hydrocarbons (CAHs) at a manufacturing facility in Belgium, Europe. The
key CAHs found in groundwater at the site include trichloroethene (TCE)
and cis 1,2- dichloroethene (DCE), as high as 1000 ppb and 450 ppb,
respectively. EHC was injected along a 160 ft (50 m) line resulting in a
permeable reactive barrier (PRB) that would intercept the CAH plume. The
PRB consisted of two rows with sixteen injection points spaced 10 ft (3 m)
apart in each row. The rows were separated by 8 ft (2.5 m).
Seven months after EHC injection, TCE remains below the groundwater
standard and DCE was reduced by 50% in the PRB. No accumulation of vinyl
chloride has been observed. Reducing conditions were successfully
established, where other substrate applications had failed in the
past.
The Challenge
The site has a history of remedial actions, including
pilot tests using molassess and phytoremediation. The molasses
treatment was successful in treating an offsite plume, however
the onsite plume treatment resulted in the accumulation and stagnation of
DCE during the usual degradation pathway for TCE (TCE, DCE, VC). This
onsite plume was the target for the pilot test with the overall remedial
goal to remove residential parcels from a register of contaminated lands.
Access was another challenge given that the plume is located below
residential houses and gardens.
The Solution
Field-Scale Pilot Study In November of 2006, a total of 13,750 lbs
(6,250 kg) of EHC was injected in 32 points to intercept the onsite plume,
resulting in a PRB with dimensions of 160 ft x 8 ft and thickness of 16 ft
(50m x 2.5m x 5m). The PRB was designed to target the deeper part of the
aquifer at depths of 16 to 32 ft bgs (5 to 10m bgs), and the injection was
performed using direct push methods. The design application rate of EHC to
soil mass was 1% in the PRB.
A PRB approach was chosen over a grid approach for the pilot test to
prevent interference with residential houses and gardens. The proposed
full scale remediation would entail multiple PRBs along the plume.
The EHC injection was completed in 11 days; approximately three
injection points were completed per day, in which each point was injected
over a depth of 16 ft (5m) at 1 ft (0.25m) intervals.
The Results
- TCE was below detection limits in the PRB within 6 months following
the application of EHC;
- No accumulation of vinyl chloride was observed;
- Cis-DCE was generated but shows a declining trend in the PRB and is
reduced by 50%, seven months after EHC injection.
- Reducing and anaerobic conditions within the PRB have demonstrated
continued performance over seven months, and are expected to continue.
- The EHC pilot test was successful in establishing reducing conditions
where other substrates had failed in the past.
Companies On This Project
ADVENTUS GROUP
