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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 21 Feb to 05 Jun, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
Minor deviations: a) ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation) and b) river water instead of an effluent/extract/mixture was used as inoculum.
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Polynt Lot No. 2103218004
- Manufacturing date: 04 Jan 2018

OTHER SPECIFICS:
- Storage at testing facility: 10 years
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): River water sampled from the Rhine near Heveadorp, The Netherlands on 15-02-2018. The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream
- Storage conditions: The river water was aerated for 7 days before use to reduce the endogenous respiration
- Storage length: 7 days
- Preparation of inoculum for exposure: River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating. The inoculum was not pre-exposed to the test substance. The river water was used undiluted

Duration of test (contact time):
60 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: As described in OECD but excluding ammonium chloride to prevent nitrification
- Solubilising agent (type and concentration if used): Tween 80, 2 mg/L
- Test temperature: 22.6 - 23.0 deg C
- pH: 8.0 on Days 0 and 28
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 300 mL BOD bottles
- Number of culture flasks/concentration: 10 x test, 10 x solvent control, 10 x inoculum blank, 6 x toxicity control
- Measuring equipment: Oxygen electrode
- Test performed in closed vessels due to significant volatility of test substance: Not applicable
- Test performed in open system: No
- Details of trap for CO2 and volatile organics if used: Not applicable

SAMPLING
- Sampling frequency: On Days 0, 7, 14, 21, 28, 42, 60
- Sampling method: Direct measurement

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes

Reference substance:
acetic acid, sodium salt
Remarks:
6.7 mg/L
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
0 d
Parameter:
% degradation (O2 consumption)
Value:
2
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
15
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
29
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
46
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
42 d
Parameter:
% degradation (O2 consumption)
Value:
71
Sampling time:
60 d
Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The tested substance should be regarded as being inherently biodegradable because >60% biodegradation was reached In the prolonged Closed Bottle test (enhanced biodegradability test, OECD 301D).
Executive summary:

Esterification products of 1,3-dioxo-2-benzofuran-5-carboxylic acid with nonan-1-ol was biodegraded by 46% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test (enhanced biodegradability test) the test substance is biodegraded by 71% at day 60. The biodegradation percentage of >60% demonstrates that test substance is inherently biodegradable. Moreover, the biodegradation in excess of 60% within the 60-day test period allows classification of the test item as not persistent.

Description of key information

Biodegradation in water: inherently biodegradable

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information

The biodegradability of the substance was estimated using the EPA model BIOWIN v4.10. The results indicate that all the 15 principal components of the assessed UVCB substance are expected to be readily biodegradable.

This is supported by experimental data which shows the substance to be inherently biodegradable, greater than 60% degradation occurring within 60 days.