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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Administrative data

Endpoint:
biodegradation in water and sediment: simulation testing, other
Remarks:
aquifer sediment degradation - degradation in groundwater
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Inhibition of Biodegradation of Hydraulic Fracturing Compounds by Glutaraldehyde: Groundwater Column and Microcosm Experiments
Author:
Rogers JD, Ferrer I, Tummings SS, Bielefeldt AR, Ryan JN.
Year:
2017
Bibliographic source:
Environ. Sci. Technol. 2017, 51, 10251−10261

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
- Principle of test: to characterize the fate and transport of substances with increased groundwater
exposure potential in aquifer sediments and to examine inhibition effects of glutaraldehyde on their biodegradation.
- Short description of test conditions: Removal kinetics were examined n the absence and presence of glutaraldehyde were measured under a range of reduction−oxidation (redox) conditions using sediment-groundwater microcosms and flow through columns. Only the results without glutaraldehyde and for 2-butoxyethanol are relevant and reported here and the anaerobic and aerobic condition results are reported in separate records
- Parameters analysed / observed: Suspended adenosine triphosphate (ATP) using a luminescence assay
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
2-butoxyethanol
EC Number:
203-905-0
EC Name:
2-butoxyethanol
Cas Number:
111-76-2
Molecular formula:
C6H14O2
IUPAC Name:
2-butoxyethanol
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: Sigma Aldrich
- Purity: >99%
Radiolabelling:
no

Study design

Oxygen conditions:
anaerobic
Inoculum or test system:
other: synthetic ground water representative of the Arapahoe Formation (Colorado, USA) with respect to major ions and pH
Details on source and properties of surface water:
Synthetic water composition:
- Chloride 14mg/L
- Bromide 1mg/L
- bicarbonate 32mg/L
- sulphate 100mg/L
- nitrate 7mg/L
- phosphate 10mg/L
- sodium 20mg/L
- potassium 8mg/L
- magnesium 14mg/L
- calcium 34mg/L
- sodium azide 1g/L
Details on source and properties of sediment:
- Details on collection (e.g. location, sampling depth, contamination history, procedure):
- Sourcing: collected from the Arapahoe Formation (Colorado, USA) between the depths of 70 and 120 m in the Denver−Julesburg Basin.
- Storage conditions: Homogenised, saturated with water, stored at 4degC.
- Textural classification (i.e. %sand/silt/clay): 92% quartz, 4.5% k-feldspar, 2% muscovite, 0.5% siderite, 1% calcite
- Organic carbon (%): 0.10 ± 0.02 % w/w
- porosity (n) 0.35
- hydraulic conductivity 3.6m/day
- attached ATP 490 ± 65 pg/g
Details on inoculum:
None used, only natural organisms in sediment
Duration of test (contact time):
232 d
Initial test substance concentration
Initial conc.:
310 mg/L
Based on:
test mat.
Remarks:
Tested as part of a mixture of typical fracking components, inlcuding isopropanol, ethylene glycol, propargyl alcohol and 2-ethylhexanol. Compositions represented averages found in fracking fluids used in basisn over period 2010-2015.
Parameter followed for biodegradation estimation:
other: ATP as an indicator of microbial activity
Details on study design:
Flow-Through Column system used. Two stainless steel columns (1 m length, 0.1 m internal diameter) were constructed with 10 sample ports consisting of stainless steel needles with Teflon Luer-lock hubslocated along their length (Figure S1; additional details in SI). Columns eere wet-packed with sediment and operated under saturated up-flow conditions. The combined groundwater and test substrate mixture were injected continuously at the base of each column
at a rate of 2.4 ± 0.2 mL/h. The average linear flow velocity was 0.018 md−1, which resulted in a water residence time of 56 d. Sampling commended at 15 d then at 30 day intervals. The injection solution was applied continuously for 232 d.

To obtain anoxic conditions, the groundwater was deaerated by purging with >99% N2 for 1 h prior to the addition of the test substrate. Anoxic microcosms were
prepared under a N2 atmosphere and sealed with Teflon lined septa.
Reference substance
Reference substance:
not required

Results and discussion

Half-life of parent compound / 50% disappearance time (DT50)
Compartment:
natural sediment
DT50:
>= 460 - <= 580 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Half lives calculated from rate constants published in source. These are only slightly faster than control abiotic degradation figures (half life 630-870 dayw), which suggest that there is little practical degradation under anoxic conditions.
Other kinetic parameters:
first order rate constant
Transformation products:
not measured
Evaporation of parent compound:
no
Volatile metabolites:
not measured
Residues:
not measured

Applicant's summary and conclusion

Validity criteria
Validity criteria fulfilled:
not specified
Executive summary:

In a study to examine the degradation in ground water formations of substances found in fracking fluids, a study using a synthetic water composition and sediment rocks obtained from an aquifer in Colorado, USA and a flow through column experimental design, found that 2 -butoxyethanol was barely degraded under anoxic conditions. For all practical purposes it can be considered that it is not degraded under these conditions.

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