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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:
15 May - 13 June 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study conducted according to OECD guideline 301 B without any major deviation
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid: viscous
Details on test material:
- Physical state: Clear colourless viscous liquid
- Lot/batch No.: 11GP0077
- Expiration date of the lot/batch: 01 January 2014
- Storage condition of test material: Room temperature in the dark
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: A mixed population of activated sewage sludge micro-organisms was obtained from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.
- Method of cultivation: The activated sewage sludge sample was washed two times by settlement and resuspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present.
- Storage conditions: The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 °C and used on the day of collection.
- Preparation of inoculum for exposure: Approximately 24 h prior to addition of the test and reference items, the vessels were filled with 2400 mL of mineral medium and 24.3 mL of inoculum and aerated overnight with CO2 free air.
- Suspended solids concentration: 3.7 g/L
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
10 mg/L
Based on:
other: carbon content
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: OECD recommended mineral medium (per litre of purified water): 85 mg KH2PO4, 217.5 mg K2HPO4, 334 mg Na2HPO4.2H2O, 5 mg NH4Cl, 22.5 mg MgSO4.7H2O, 27.5 mg CaCI2, 0.25 mg FeCI3.6H2O
- Source/preparation of dilution water: Reverse osmosis purified and deionised water
- Test temperature: 21 °C
- pH (at start of test): 7.6; pH (at end of test): 7.6 (controls) and 7.5 (test)
- Suspended solids concentration: 30 mg/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: Test culture vessels (5 L); each containing 3 L of solution
- Number of culture flasks/concentration: Duplicate for test, inoculum blank and procedure control and single vessel for toxicity control
- Method used to create aerobic conditions: The test vessels were sealed and CO2-free air bubbled through the solution at a rate of 30 to 100 mL/min per vessel and stirred continuously by magnetic stirrer. The CO2-free air was produced by passing compressed air through a glass column containing self-indicating soda lime (Carbosorb) granules.
- Details of trap for CO2 and volatile organics if used: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water.

MEASURING EQUIPMENTS:
- The samples were analysed for CO2 using a Tekmar-Dohrmann Apollo 9000 TOC analyser, a Shimadzu TOC-VCSH TOC analyser and a Shimadzu TOC-LCSH TOC analyser.
- The pH was measured using a WTW pH/Oxi 340I pH and dissolved oxygen meter.
- Temperature was measured and recorded with a sensor connected to a data logger.

SAMPLING
- Sampling frequency: Samples (2 mL) were taken from the first CO2 absorber vessels on Days 0, 2, 6, 8, 10, 14, 21, 28 and 29. The second absorber vessels were all sampled on Days 0 and 29. All samples were analysed for CO2 immediately.
- On Day 28, 1 mL of concentrated hydrochloric acid was added to each vessel to drive off any inorganic carbonates formed. The vessels were resealed, aerated overnight and the final samples taken from both absorber vessels on Day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes (duplicate); containing inoculum mineral medium and a glass slide
- Procedure control: Yes (duplicate); containing reference substance (sodium benzoate) in inoculated mineral medium and a glass slide
- Toxicity control: Yes (single); containing test item on a glass slide and reference substance (sodium benzoate) in inoculated mineral medium
Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
10 mg C/L; purity: 99 %

Results and discussion

Preliminary study:
No data
Test performance:
No data
% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
36
Sampling time:
28 d
Details on results:
Initial test material concentration: 10 mg C/L
- Total carbon = 10.02-10.09 mg/L
- Inorganic carbon: -0.06 to +0.06 mg/L
- IC content (% of TC): 0-1
- % biodegradation on Day 14: 9 %
- % biodegradation (corrected) on Day 28: 36 %

BOD5 / COD results

Results with reference substance:
- % biodegradation on Day 2: 61 %
- % biodegradation on Day 14: 93 %
- % biodegradation on Day 28: 87 %

Any other information on results incl. tables

Table 5.2.1/1: Percentage biodegradation values

Day

% Degradation

sodium benzoate

procedure control

% Degradation

test item

% Degradation

test item plus sodium benzoate

toxicity control

0

0

0

0

2

61

4

25

6

73

4

26

8

80

3

27

10

78

8

26

14

93

9

30

21

88

24

34

28

87

31

30

29*

84

36

43

*Day 29 values corrected to include any carry-over of CO2 detected in Absorber 2

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
total CO2 evolution in inoculum blank on Day 28: 31.40 mg/L; IC content in test vessel at Day 0: < 5 % of TC content; differences of replicate values at Day 28: < 20%; degradation in reference and toxicity controls at Day 14 were 93 and 30 %, respectively
Interpretation of results:
other: under the test conditions, the test item was not considered as readily biodegradable
Conclusions:
Under the test conditions, the test item, was not considered as readily biodegradable.
Executive summary:

In a ready biodegradation study performed according to OECD Guideline 301 B and GLP, the test item, was tested at concentrations of 10 mg C/L and the inoculum was activated sewage sludge, domestic. The degradation of the test material was assessed by the determination of the CO2 evolution. One vessel for toxicity control and duplicate vessels for test treatments, inoculum blank, and reference (sodium benzoate) were measured.

At 10 mg C/L test concentration, only 36 % degradation was attained after 28 days.

The total CO2 evolution in the inoculum blank on Day 28 was 31.40 mg/L. The IC content of the test item suspension in the mineral medium at the start of the test was < 5 % of the TC content. The differences of replicate values at Day 28 were < 20 %. The toxicity control attained 30 % degradation after 14 days thereby confirming that the test item was not toxic to the sewage treatment micro-organisms. Sodium benzoate attained 93 % degradation after 14 days thereby confirming the suitability of the inoculum and test conditions.

Under the test conditions, the test item, was not considered as readily biodegradable.