Frac-In technology

1. The Effects of Hydraulic/Pneumatic Fracturing Enhanced Remediation (FRAC IN) at a Site Contaminated by Chlorinated Ethenes Ondřej Lhotský, Jan Kukačka, Jan Slunský, Kristyna Markova, Tomáš Cajthaml

3. Frac-In technology • Combines Direct-Push drilling with pneumatic and hydraulic fracturing to inject remediation agentsin to low-permeable contaminated soils • The injected material consists of a tailor made remediation suspensions such as different scale zerovalent iron, carbon sources for bacteria and sand

4. Pilot test of the Frac-In on the site in Western Czechia - The Locality • Old metalworkswith chlorinated ethenes (PCE is dominant)contamination in both unsaturated and saturated zone • Complex geology– quaternary deposits formed by a mixture of loamy to sandy clays with a significant amount of existing preferential flow pathswith the permeability in range of 10-5 to 10-6 m/s • Pilot spot selected and monitoring system (consisting of 9 wells) installed based on previous MIP survey and other works

5. Conceptualsitemodel • Thin uncontaminated backfill • Highly contaminated unsaturated zone with fracture network filled with PCE DNAPL • PCE slowly drowning in to the saturated zone causing its contamination • PCE dissolution and its slow partial dechlorination and transport via existing preferential flow paths and difusion Frac In injections in to both unsaturated and saturated zone in order to widen current fracture system and fill it with reactive materials Nitrogen used for pneumatic fracturing Mixture of sand, milled iron and sulfidizednZVI used to fill the fractures Dried whey injected afterwards in to the fractures to provide carbon source for bacteria

6. FRAC IN Injections • In total: • 9 injection points • 45 successful injection horizons • 5,5 m3of suspension • 1700 Kg of milled Fe and sand • 35 Kg of SnZVI • 5,5 m3of hydraulic/rinse fluid • 300 kg of dried wheywith pH stabiliser • In 5 days 4 people • Reasonable performance is 2-3 points with 6-8 horizons per day • Based on the results the radius of influence varied from 2 to 6 m, with typical ROI around 4 m Approx. 50% of material injected in to the unsaturated zone

7. FRAC IN Injections – effects on thegroundwatercontamination

8. FRAC IN – long term effects – physico-chemical parameters MEAN VALUES FROM ALL THE MONITORING WELLS • pH remained in the neutral range • Eh decreased though less than expected, lower Eh kept on site for long period of time • Groundwater depth decreased due to draught it only increased again after the winter

9. FRAC IN – long term effects – chlorinated ethenes MEAN VALUES FROM ALL THE MONITORING WELLS • Significant PCE decrease from mean values round 10 mg/L to 2 mg/L • TCE increased right after the Frac in, due to mobilisation and quick conversion of PCE • sDCE slowly rising after the FRAC IN reaching very high values one year after injection • VC appeared after FRAC IN and raised slowly, significant increase after the winter

10. FRAC IN – long term effects – gaseous dechlor. products MEAN VALUES FROM ALL THE MONITORING WELLS • Methane productionfairly limited, increase after winter • Significant (long term) acetylene production after the FRAC IN caused by chemical reduction of CVOCs • Ethene appeared due to biodegradation after FRAC IN and raised slowly, significant increase • after the winter

11. FRAC IN – long term effects – TOC, Sulphates, iron MEAN VALUES FROM ALL THE MONITORING WELLS • TOC increased significantly due to whey injection, later decreased to increase again after • the winter • Continuous decrease of sulphates after the FRAC IN caused by its reduction

12. FRAC IN – long term effects – Bacteria MEAN VALUES FROM ALL THE MONITORING WELLS • vcrA (vinylchlorid reductase) and DHC-RT (Dehalococcoides) qPCR markers decreased right after the FRAC IN (probably due to short term toxicity of the SnZVI to these bacteria) to increase significantly later on with aditional acceleration after the winter. • Current population of bacteria capable of reductive dechlorination is very high • Concentrations of cultivable bacteria increased significantly after FRAC IN and remained high later on • Universal 16SRNA qPCR marker of overall bacterial abundance increased after FRAC IN and remained elevated later on

13. FRAC IN – long term effects – Otherrelevantbacteria MEAN VALUES FROM ALL THE MONITORING WELLS • Significant increase of bacteria metabolising sulphur and iron capable of partial reductive dechlorination(Desulfitobacterium, Geobacter) after FRAC IN after winter theirconcentrations dropped but remained elevated compared to pre FRAC IN • Surprisingly Gallionellaferrugineairon oxidising bacteria was inhibited by the FRAC IN

14. Conclusions -Conceptualsitemodel Right after the FRAC IN One year after the FRAC IN • Drainage of rainwater is causing increase of both CVOCs and organic carbon in groundwater • PCE significantly decreased in GW • sDCE very high but is transformed further to VC and ethene • Very high bacterial abundance and dechlorination activity • Fractures widened and partly filled with Fe0 that reacted with PCE to form acetylene • High concentrations of organic carbon • PCE mobilised and partly converted to TCE • sDCE and VC still low • Low quantities of bacteria Triggered process will continue in the future !!!

15. Thank you very much for your Attention! Ondřej Lhotský, lhotsky@dekonta.cz For more information visit: www.fracin.eu And poster called: Frac-In: Development and Testing of a Technology forCombined Direct Push and FracturingofContaminatedsoil 4C-14