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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2015
Report Date:
2015

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
gas under pressure: liquefied gas
Details on test material:
- Purity: 99.7944% (v/v)

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: Secondary effluent of city sewage treatment plant
- Preparation of inoculum for exposure: The collected secondary effluent was filtered through a filter paper (No. 2) and the filtrate was used as inoculum. The inoculum was kept under aerobic condition until used.
- Preparation of mineral medium: Each 5 mL of solution A, B, C and D prescribed by the Closed Bottle Test were mixed and made up to 5 L with purified water. After the preparation, it was aerated strongly for 20 minutes and allowed to stand for 21 hours at test temperature.
- Addition of inoculum: The 0.05 mL per liter of the inoculum was added into the mineral medium.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
6.25 mg/L
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
test mat. analysis
Details on study design:
Preparation of test solutions: The following test solutions in 35 test bottles were prepared and incubated.
- Inoculum blank: Each test bottle was filled with the inoculated mineral medium.
- Abiotic control (water + test item): Each test bottle was filled with purified water and 2.5 mL of the test item saturation solution (test item 0.625 mg) was added into it by microsyringe, so that the concentration of the test item was 6.25 mg/L
- Test suspension (inoculum + test item): Each test bottle was filled with the inoculated mineral medium and 2.5 mL of the test item saturation solution (test item 0.625 mg) was added into it by microsyringe, so that the concentration of the test item was 6.25 mg/L
- Procedure control (inoculum + sodium benzoate): Each test bottle was filled with 3.00 mg/L sodium benzoate solution prepared with the inoculated mineral medium.

Incubation temperature: 20±1°C
Observation of test solution: During the incubation period, the appearance of the test solutions was observed once a day.
Measurement of dissolved oxygen (DO): DO of each test solution except the abiotic control was analysed in accordance with diaphragm electrode method, and biochemical oxygen demand (BOD) was calculated.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradationopen allclose all
Key result
Parameter:
% degradation (test mat. analysis)
Value:
2
Sampling time:
28 d
Remarks on result:
other: GC analysis
Key result
Parameter:
other: % biodegradation
Remarks:
BOD
Value:
5
Sampling time:
28 d
Details on results:
The mean percentage biodegradation by BOD and that of the test item after 28 days were 5% and 2%. Additionally, no peak except for the test item peak was detected on GC chromatogram, and this result suggested that no converted product was generated from the test item. In conclusion from above, the test item was considered to be not biodegraded under the test condition of this study.

BOD5 / COD results

Results with reference substance:
Percentage biodegradation of sodium benzoate by BOD after 14 days is 80 and 73%

Any other information on results incl. tables

Analytical results of the test solutions after 28 days were as follows.

___ Abiotic control Test suspension Theoretical amount
1 2 1 2
BOD mgO2/L _ _ 0.19 0.32 5.49
Residual amount and percentage residue of test item (GC) mg 0.635 0.643 0.632 0.616 0.625
% 102 103 101 98 _

Percentage biodegradations were as follows.

___ Test suspension
1 2 Mean value
Percentage biodegradation by BOD % 3 6 5
Percentage biodegradation of test item (GC) % 1 4 2

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item was not readily biodegradable as the pass level of 60% BOD was not achieved during the test.
Executive summary:

This study was aimed at evaluating the biodegradability of the test substance by microorganisms according to the closed bottle test (OECD guideline 301D).

Conditions of incubation are as follows,

Concentration of test item: 6.25 mg/L

Concentration of inoculum: 0.05 mL/L

Volume of test solution: 100 mL

Incubation temperature: 20±1°C

Incubation method: Stationary incubation in sealed condition

Incubation duration: 28 days (under dark condition)

Measurement and analysis for calculation of percentage biodegradation: Measurement of dissolved oxygen by diaphragm electrode method (DO) and Determination of test item by gas chromatography (GC). The mean percentage biodegradation by BOD and that of the test item after 28 days were 5% and 2%. The test item was not readily biodegradable as the pass level of 60% BOD was not achieved during the test.