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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:
16 January 2018 - 20 February 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

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

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Version / remarks:
adopted 23 March 2006, corrected 26 September 2014
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
liquid: viscous
Specific details on test material used for the study:
Vapour pressure: 8 hPa (6mm hg) at 20°C
Solubility in water: insoluble

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Preparation of inoculum for exposure: The freshly obtained sludge was kept under continuous aeration until further treatment.The concentration of suspended solids was determined to be 3.1 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (30 minutes) and the liquid was decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
20 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
inorg. C analysis
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium according to OECD 310, made with Milli-RO water (Tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Milli-Q), containing carbon levels < 500 ppb).
- Test temperature: 19 - 20 °C
- pH at start of test: 7.4 - 7.8
- Continuous darkness: yes
- Shaking: orbital shaker, with a shaking rate sufficient to keep the vessel well mixed and in suspension.

TEST SYSTEM
- Culturing apparatus: well-sealed glass vessels, headspace to liquid ratio of 1:2 (107 mL test medium in 160 mL-capacity vessel).
- Total number of culture flasks/concentration: 5
- Method used to create aerobic conditions: a heaspace of air
- Measuring equipment: TOC analyser
- Test performed in closed vessels: yes

SAMPLING
- Sampling frequency: on day 1, 7, 14, 21,28 for inoculum blank and test item; on day 1, 7, 14 for the procedure control and the toxicity control; on day 1 and 28 for the abiotic control. For all treatment groups, sampling was done in three vessels except for the last sampling day on which it was performed in five vessels.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Only inoculated medium.
- Abiotic sterile control: Untreated medium and sterilizing agent (1 mL of a solution containing 10 g/L of HgCl2) and test item
- Toxicity control: Inoculated medium, reference item, test item
- Procedure control: Inoculated medium and reference item.

STATISTICAL METHODS: no statistical analysis was performed
Reference substance
Reference substance:
other: Octan-1-ol

Results and discussion

% Degradation
Key result
Parameter:
% degradation (inorg. C analysis)
Value:
21
Sampling time:
28 d
Remarks on result:
other: mean of replicate vessels tested
Details on results:
- The TOC content of the test item was determined to be 74% and the ThIC of the reference item (Octan-1-ol) was calculated to be 0.74 mg/mg.
- For biodegradation in individual vessels see table 1.
- In the abiotic control no degradation of the test item was observed.
- In the toxicity control more than 25% biodegradation occurred within 14 days (29%, based on ThIC). Therefore, the test item was assumed not to inhibit microbial activity.

BOD5 / COD results

Results with reference substance:
The reference item was degraded for 63% (mean of repliacte vessels tested) after 14 days.

Any other information on results incl. tables

Acceptability of the Test

1. The reference item was biodegraded by at least 60% (mean: 63%) within 14 days.

2. The mean amount of TIC present in the inoculum blanks at the end of the test was < 3 mg C/L (1.4 mg C/L).

Since all criteria for acceptability of the test were met, this study was considered to be valid.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Based on the results of a Headspace Test, Setalux 7002 BX-55 is not readily biodegradable (21% after 28 days).