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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
Study period:
13 May - 11 Jun 1997
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study with acceptable restrictions: The difference of extremes of replicate values of the removal of the test chemical is more than 20%. However, as all replicates show biodegradation values of > 60% this differences are considered as negligible.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1997
Report Date:
1997

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
The difference of extremes of replicate values of the removal of the test chemical is more than 20%
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Only trade name given.
- Physical state: yellow liquid
- Analytical purity: no data
- Lot/batch No.: N558331
- Storage condition of test material: at room temperature in the dark
- Other: Stable under storage conditions; 77.10% TOC content

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Municipal sewage treatment plant: Waterschap de Maaskant, s'Hertogenbosch, The Netherlands
- Preparation of inoculum for exposure: Before use, the sludge was allowed to settle for at least 30 min and the liquid decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
- Pretreatment: The sludge was kept under continuous aeration until further treatment.
- Initial cell/biomass concentration: From the supernatant of the sludge the heterotrophic microbial colony count was determined to be
6.6 x 10³ cells/mL.
Duration of test (contact time):
29 d
Initial test substance concentration
Initial conc.:
15.5 - 15.6 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium
- Test temperature: 20 - 21.5 °C
- pH: 7.4 - 7.7
- Aeration of dilution water: The mixture of mineral components, Milli-Q water and inoculum was aerated with CO2-free air overnight to purge the system of CO2.
- Suspended solids concentration: 4.1 g/L
- other: The test solutions were continuously stirred during the test.

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: CO2-free air was sparged through the scrubbing solutions at a constant rate.
- Details of trap for CO2: Three CO2-absorbers (bottles filled with 100 ml 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle. The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate.

SAMPLING
- Sampling frequency: on day 3, 6, 8, 10, 15, 20, 24, 29
- Sampling method: The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCL. On the 28th
day, the pH of the test suspensions was measured and 1 ml of concentrated HCL was added to each bottle. The bottle were aerated overnight to
drive off CO2 present in the test suspension. The final titration was made on day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2 replicates
- Toxicity control: yes, 1 replicate
Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
71.9 - 99.8
Sampling time:
29 d

BOD5 / COD results

Results with reference substance:
Degradation: 74.5% after 8 days, 60% pass level was reached.

Any other information on results incl. tables

Table 1: Percentage biodegradation of test substance, reference substance and toxicity control

Day

Test

Substance

(% degradation)

Reference substance

(% degradation)

Toxicity control

(% degradation)

Replicate 1

Replicate 2

Ø

3

4.4

8.6

6.5

17.2

13.1

6

11.8

16.9

14.35

41.5

27.4

8

38.4

49.7

44.05

74.5

56.5

10

50.4

66.9

58.65

88.7

72.9

15

58.4

77.9

68.15

98.2

83.2

20

66.6

83.9

75.25

102.6

87.1

24

70.2

91.2

80.7

106.5

89.3

29

71.9

97.0

84.45

110.9

94.2

29

71.9

99.7

85.8

112.0

95.3

29

71.9

99.8

85.85

112.0

95.7

 

 

 

Applicant's summary and conclusion

Validity criteria fulfilled:
no
Remarks:
The difference of extremes of replicate values of the removal of the test chemical is more than 20% on day 24 and 29.
Interpretation of results:
readily biodegradable