2-butoxyethanol

Biodegradation in water and sediment: simulation tests

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

Test material information

Constituent 1

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.