Registration Dossier

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:
19 Oct - 17 Nov 2017
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 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
July 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Karlsruhe, Germany

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: AZV Staufener Bucht, sampled on 17 Oct 2017
- Storage length: 1 day between sampling and start of incubation of the test item
- Preparation of inoculum for exposure: drying at 105 °C for 5 hours, washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge
- Concentration of sludge: 30 mg dry solids/L
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:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: required range of 20.6 – 24.0 °C.
- Aeration of dilution water: tolerated range of 1.6 – 5.5 bubbles/second (counted bubbles: 2.4 – 5.1 bubbles/second)
- Suspended solids concentration: 30 mg dry solids/L

TEST SYSTEM
- Culturing apparatus: Gas wash bottles (2000 mL volume)
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: The CO2-free air production system consists of an air compressor, three 1000 mL gas wash bottles filled with dry soda lime in series followed by one bottle filled with 0.1 M NaOH (sodium hydroxide). At the end of the system is one gas wash bottle filled with demineralised water, followed by an empty one to catch any drops of condensation water. A color change of the soda lime from white to blue indicates that the CO2 absorption capacity is depleted. The CO2-free air is passed on to an air distributor with two input and 22 output channels and through PE-tubes.
- Measuring equipment/method: Degradation is followed by determining the carbon dioxide produced and absorbed to sodium hydroxide via IC-measurement (IC = inorganic carbon). Degradation is followed by determining the carbon dioxide produced and absorbed to sodium hydroxide via measurement of the inorganic carbon (IC). IC measurement was performed with a total carbon analyser (TOC-L Shimadzu) by purging the inorganic carbon with H3PO4 (25%) using a nondispersive infrared (NDIR) detector.

SAMPLING
- Sampling frequency: Sampling for IC measurement took place on days 0, 4, 7, 11, 14, 21, 28 and 29.
- Sampling method: Sampling was performed through the lateral connecting pieces through the butyl rubber septum using 5 mL PE syringes.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, three bottles
- Toxicity control: yes, one bottle
- Reference substance: yes, three bottles
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
82.2
Sampling time:
28 d
Details on results:
The test item reached the criteria for ready biodegradability according to the OECD criteria (60% of ThCO2 within a 10-d window).
The degradation extent in the toxicity control was 61.2% within 14 days. The test material is therefore considered to have no inhibitory effect on the inoculum according to the criterion of the guideline.
For details on biodegradation rates, please refer to Table 1 in section "Any other information on results incl. tables".

BOD5 / COD results

Results with reference substance:
The reference substance reached the pass level for ready biodegradability within 4 days. The degradation after 28 days was 89.5-97.8%.

Any other information on results incl. tables

Table 1: Ultimate biodegradation after x days [% of ThCO2]

Reactor

Days

0

4

7

11

14

21

28

29

7

Test flasks

0

6.7

25.0

56.3

67.6

86.2

77.2

77.5

8

0

8.1

39.7

64.0

70.2

93.0

89.9

88.9

9

0

7.8

29.1

55.1

63.3

81.0

79.4

80.3

4

Reference flasks

0

68.7

84.1

86.3

87.3

101.4

89.5

89.9

5

0

80.9

89.9

92.2

92.2

106.6

97.8

99.3

6

0

73.9

86.4

86.3

88.9

107.2

96.3

98.3

10

Toxicity control

(Test item + Reference item)

0

37.3

45.8

53.9

61.2

84.4

77.9

78.8

Table 2: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.

 < 20%

 yes

Percentage degradation of the reference compound has reached the pass levels by day 14.

 > 87%

 yes

The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.

 > 61%

 yes

The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.

< 5%

 yes

The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.

 29.9 mg/L

 yes

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
For further details please refer to "Any other information on results incl. tables."
Interpretation of results:
readily biodegradable