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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 August 17,2009 to September 24,2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
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. T408209159
- Manufacturing date: 08 Jun 2009
- Expiration date of the lot/batch: 08 Jun 2010

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Keep container tightly closed. Keep in a dry, cool and well ventilated place.
- Stability under test conditions: The test material reacts forming the corresponding acid: 1,2-Cyclohexanedicarboxylic acid, 4-methyl- (in water and light at room temperature).
- Storage at testing facility: 5 years
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum: Inoculum of the aqueous phase of non adapted activated sludge
- Laboratory culture:Municipal sewage treatment plant, D-31137 Hildesheim
- Reasons for the selection: Activated sludge from the sewage plant at Hildesheim is well suited as it receives predominantly municipal sewage and ha rdly any industrial chemical waste.
- Preparation of inoculum for exposure:
- Pretreatment:The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was re-suspended in mineral salts medium and was maintained in an aerobic condition by aeration for 4 hours. Thereafter the sludge was homogenized with a blender. The supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 5 days.
- Concentration of sludge:10 mL/L were used to initiate inoculation.
- Colony forming units in the test vessels : 10E7 - 10E8 CFU/L
- Water filtered: yes , autoclaved tap water
Duration of test (contact time):
ca. 28 d
Initial conc.:
40 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Application: Once at test start
- Test vessels: Brown glass bottles (volume 500 mL)
- Test volume: 250 mL
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature:20.0 - 21.0 °C
- pH: 7.43 +/- 0.1
- pH adjusted: no
- Suspended solids concentration:
- Continuous darkness: yes , in an incubator
- Dispersion treatment: continuous stirring


TEST ITEM:
ThOD: 1.99 mg O2/mg test item
Test concentration: 40 mg/L
ThOD in the test vessel: 79.6 mg O2/L
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
ca. 2
Sampling time:
28 d
Details on results:
- Theoretical Oxygen Demand:
The biodegradation in % was calculated based on the ThOD of 1.99 mg O2/mg test item.
- Colony Forming Units of the Inoculum:
Colony forming units (CFU) of the inoculum were determined at test start by standard dilution plate count: 5.7E9 CFU/L
- Results of the Functional Control:
The pass level of a biodegradation > 60 % was reached after 2 days. The validity criterion that the degradation should be > 60 % after 14 days was fulfilled.

Results with reference substance:
In order to check the activity of the test system sodium benzoate was used as functional control. The pass level > 60 % was reached after 2 days. The biodegradation rate reached 90 % within 14 days.

In the toxicity control containing both test and reference item 39 % degradation occurred within 14 days. At this point the plateau was reached. The degradation of the reference item was not inhibited by the test item.

 

The biodegradation of the test substance did not reach the 10 % level (beginning of biodegradation) within 28 days. After 28 days the mean biodegradation was 2 %.

 

Biodegradation [%]

 

Study Day [d]

 

Replicate

7

14

21

28

Test Item
40 mg/L

1

0

0

0

0

2

5

2

4

4

Functional Control
45 mg/L

1

84

90

97

100

Toxicity Control
40 mg/L Test Item +
45 mg/L Reference Item

1

36

39

40

39

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
After 28 days the mean biodegradation was 2% and the test substance must be regarded as not readily biodegradable. A toxicity control containing both test and reference substances demonstrated that degradation of the reference item was not inhibited by the test substance indicating that the test substance is not inhibitory to STP microorganisms.

Executive summary:

Ready biodegradability of 4-MHHPA by a non-adapted activated sludge has been investigated according to OECD/EU test methods using a Manometric Respirometry Test. After 28 days the mean biodegradation was 2% and the test substance must be regarded as not readily biodegradable. A toxicity control containing both test and reference substances demonstrated that degradation of the reference item was not inhibited by the test substance indicating that the test substance is not inhibitory to STP microorganisms.

Description of key information

Ready biodegradability: 2% in 28 days

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Ready biodegradability of 4-MHHPA by a non-adapted activated sludge has been investigated according to OECD/EU test methods using a Manometric Respirometry Test. After 28 days the mean biodegradation was 2% and the test substance must be regarded as not readily biodegradable. A toxicity control containing both test and reference substances demonstrated that degradation of the reference substance was not inhibited by the test substance indicating that the test substance is not inhibitory to STP microorganisms.