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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-12-18 to 2018-01-19
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO 10707 Water quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
- Physical state: powder/solid
- Appearance: white powder
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Analytical purity: 99.86%
- Source and lot/batch No.of test material: 397451
- Expiration date of the lot/batch: 2018-02-07 (retest date)
- Purity test date: 2017-09-05 (certificate of analysis release date)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: In refrigerator (2-8°C)
- Solubility in water: 20 g/L

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source: Municipal sewage treatment plant receiving predominantly domestic sewage, 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands.
- Storage conditions: Sludge was kept under continuous aeration until further treatment
- Preparation of inoculum for exposure: The secondary effluent was filtered through a coarse filter paper and the first 200 mL were discarded. The filtrate was be kept aerated until inoculation.
- Pretreatment: no
- Concentration of sludge: 4 mL filtrate of secondary effluent per litre of final volume.
- Water filtered: Tap-water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
2 mg/L
Based on:
test mat.
Initial conc.:
5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Tap-water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).
* mineral stock solution A: 8.5 g KH2PO4, 21.75 g K2HPO4, 67.20 g Na2HPO4.12H2O, 0.5 gNH4Cl dissolved in 1 L Milli-Q water, pH 7.4 ± 0.2
* mineral stock solution B: 22.50 g MgSO4.7H2O dissolved in 1 L Milli-Q water
* mineral stock solution C: 36.4 g CaCl2.2H2O dissolved in 1 L Milli-Q water
* mineral stock solution D: 0.25 g FeCl3.6H2O dissolved in 1 L Milli-Q water
* Final test medium: 1 mL of solutions A to D per L of test medium
- Additional substrate: no
- Test temperature: 19-21°C
- pH: 7.1-7.2, At the start of the test
- pH adjusted: no
- Aeration of dilution water: The test solutions were continuously aerated and stirred during the test.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 250-300 mL BOD bottles with glass stoppers.
- Number of culture flasks/concentration: 2
* test substance and inoculum: 2 replicates
* inoculum blank: 2 replicates
* positive control: 2 replicate
* toxicity control: 2 replicate
- Method used to create aerobic conditions: The mineral medium was left at test temperature to obtain an oxygen-saturated solution at the start of the test. Care was taken to ensure the solutions were not supersaturated with oxygen.
- Measuring equipment: WTW oxygen meter supplied with a WTW CellOx 325 oxygen electrode, electrolyte type ELY/G.

SAMPLING
- Sampling frequency: In duplicate; immediately at the start of the experiment (day 0), and on day 7, 14, 21 and 28.
- Sampling method: no data

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, with only inoculum
- Toxicity control: yes, with test item, reference substance (lowest concentration), and inoculum
- Procedure control: yes, with reference item and inoculum

Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

Test performance:
- In the toxicity control more than 25 % degradation occurred within 14 days (51% based on ThCO2). Therefore, the test substance was assumed to be not inhibitory on microbial activity.
- Oxygen depletion in the inoculum blank was less than 1.5 mg O2/L after 28 days (0.65 mg O2/L).
- The residual concentration of oxygen in the test bottles was > 0.5 mg/L at any time.
- Differences between duplicate biodegradation values (expressed as mg O2/L) were less than 20% (7-8%).
- In the procedure control, sodium acetate was degraded by at least 60% (79%) within 14 days.
% Degradationopen allclose all
Key result
Parameter:
% degradation (CO2 evolution)
Value:
94
Sampling time:
28 d
Remarks on result:
other: initial concentration of 2.0 mg/L
Key result
Parameter:
% degradation (CO2 evolution)
Value:
60
Sampling time:
28 d
Remarks on result:
other: initial concentration of 5.0 mg/L
Details on results:
The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed 94% and 60% biodegradation of 1,4-Dioxan-2-one (PDO Monomer) (based on ThOD) at the concentration of 2.0 mg/L and 5.0 mg/L, respectively. In addition, at a concentration of 2.0 mg/L biodegradation of at least 60% was reached within 14 days of biodegradation exceeding 10%. No explanation can be given for the decreasing biodegradation pattern at 5.0 mg/L as of day 21 of the test.

BOD5 / COD results

Results with reference substance:
The positive control item was biodegraded by at least 60% (79%) within 14 days, confirming suitability of the activated sludge.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
A 28-d ready biodegradability test (OECD 301D, modified Sturm test) using unadapted activated sludge from a predominantly domestic waste water treatment plant indicated that 1,4-dioxan-2-one was readily biodegradable under the conditions of the test (initial concentration of 2 and 5 mg/L). The test substance showed 94% and 60% biodegradation (at the concentration of 2.0 mg/L and 5.0 mg/L, respectively). The test substance did not inhibit microbial activity at the concentration used in the test. The results of the test can be considered reliable without restriction.