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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Data waiving:
study technically not feasible
Justification for data waiving:
other:
Justification for type of information:
Due to the low solubility of the substance (0.2-0.4 mg/L) the study was technically not feasible.
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
28 August 2013 - 26 September 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test method according to EC C.4-D and OECD 301F. GLP study.
Qualifier:
according to
Guideline:
other: EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Qualifier:
according to
Guideline:
other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Source of inoculum/activated sludge: Aeration tank of Sewage Treatment Plant "Czajka" Warsaw.
- Storage conditions: The coarse particles were removed by filtration. Such prepared sludge was washed in the medium and was placed in laboratory scale unit where the aerobic conditions were maintained by means of an intense aeration with compressor and aerators.
- Preparation of inoculum for exposure: The concentrated sludge was suspended in mineral medium to yield a concentration of 3-5 g suspended solids/l and it was aerated until application. After complete re-suspension was achieved, a sample was withdrawn just before use for the determination of the dry weight of the suspended solids.
- Pretreatment: Inocula was pre-conditioned to the experimental conditions. Pre-conditioning consisted of aerating activated sludge in mineral medium for 2 days at the test temperature of 22 ºC.
- Initial biomass concentration: 30 mg/L SS
Test type:
other: Readily biodegradation
Water media type:
freshwater
Limit test:
no
Total exposure duration:
28 d
Test temperature:
21.8 ± 0.2 °C
pH:
6.91-7.08
Nominal and measured concentrations:
100 mg/L loading rate.
Details on test conditions:
TEST SYSTEM
- Test vessel: Thermo-cabinet WTW TS 606 CZ-G/3-VAR
- Material, size, headspace, fill volume: 164 ml volume
- Aeration: aerobic conditions
- No. of organisms per vessel: 30 mg/L SS inoculum
- No. of vessels per concentration (replicates):
Test solution: 3 replicates, each containing 100 mg/L loading rate test item and 30 mg/L SS inoculum.
Inoculum blank: 3 replicates, each containing 30 mg/L SS inoculum.
Procedure control: 3 replicates, each containing 100 mg/L reference item (sodium acetate) and 30 mg/L SS inoculum.
Toxicity control: 3 replicates, each containing 100 mg/L loading rate test item, 100 mg/L reference item (sodium acetate) and 30 mg/L SS inoculum.

TEST MEDIUM / WATER PARAMETERS
The double-distilled water was taken from redistillation set. The mineral composition was in accordance with the guidelines. Since the test item is poorly water soluble, CNSL was added directly to the mineral medium at the flask preparation stage on a weight basis.

OTHER TEST CONDITIONS
- Adjustment of pH: No.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
Biodegradation % based on oxygen consumption. The consumption of oxygen was determined from the change in pressure in the apparatus. The carbon dioxide, evolved during test item degradation, was absorbed in a solution of potassium hydroxide. The amount of oxygen taken up by the test item (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of determined COD of the test item.

TEST CONCENTRATIONS
- Test concentrations: 100 mg/L loading rate
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: readily biodegradation
Details on results:
The NOEC of CNSL was determined to be 100 mg/L loading rate since the substance degrades well (83.8% of biodegradation at 28 days) and did not inhibit the degradation of microorganisms in the toxicity test (69.3% of biodegradation after 28 days) up to 100 mg/L loading rate.
The effect concentration exceeds the solubility of substance in test medium. Based on the solubility test, the water solubility of CNSL is 0.2-0.4 mg/L. Nevertheless, since the substance is an UVCB, the loading rate of 100 mg/L has been taken into account for the effect concentration.

Sample oxygen uptake: biodegradability:

Average: 3 flasks

Time (days)

3

5

7

9

12

14

16

18

21

23

25

28

Test item O2 uptate (mg/L)

71.2

113.8

159.2

188.3

213.5

224.9

233.4

239.8

248.1

252.7

256.7

262.8

Blank test O2 uptake (mg/L)

19.1

23.4

25.6

28.4

29.8

32.0

33.0

32.8

34.7

34.6

36.5

38.9

Reference item O2 uptake (mg/L)

65.0

82.0

90.2

95.0

98.9

102.1

105.0

106.8

108.6

108.4

109.4

111.2

Toxicity control O2 up. (mg/L)

66.8

118.2

148.9

172.4

205.5

226.4

238.8

251.9

263.1

268.1

272.0

278.2

Corrected test item O2 up. (mg/L)

52.1

90.4

133.6

159.8

183.8

192.9

200.4

207.0

213.4

218.1

219.6

223.8

Reference item % degradation*

58.9

75.2

82.8

85.4

88.6

89.9

92.2

94.9

94.7

94.6

93.4

92.6

Test item % degradation**

19.5

33.8

50.0

59.9

68.8

72.2

75.1

77.5

79.9

81.7

82.3

83.8

Toxicity control % degradation***

14.8

27.5

35.7

41.7

50.9

56.3

59.6

63.5

66.2

67.7

68.3

69.3

*BOD/CODx100, where COD = 0.78 mgO2/L

** BOD/CODx100, where COD = 2.67 mgO2/L

*** BOD/CODx100, where COD = 345 mgO2/L

Conclusions:
The 28d-NOEC for activaed sludge of the test item was determined to be 100 mg/L loading rate (based on biodegradation).
Executive summary:

A ready biodegradability manometic respirometry test was performed according to EC C.4 -D and OECD 301F. Test item CNSL was incubated for 28 days at a concentration of 100 mg/L (loading rate) with 30 mg/L SS activated sludge inoculum under aerobic conditions in a mineral medium. Additionally, a toxicity test run in parallel (100 mg/L test item with 100 mg/L reference substance and 30 mg/L SS activated sludge inoculum) to check the possible inhibitory effect of the test item. The NOEC (28d) of CNSL was determined to be 100 mg/L loading rate since the substance degraded well (83.8% of biodegradation at 28 days) and did not inhibit the degradation in the toxicity test (69.3% of biodegradation after 28 days) up to 100 mg/L loading rate.

Description of key information

Data waiving (study technically not feasible): Due to the low solubility of the substance (0.2-0.4 mg/L) the study was technically not feasible.

Supporting study: Test method EC C.4-D, OECD 301F. GLP study. The 28d-NOEC for activated sludge of the test item was determined to be 100 mg/L loading rate (based on biodegradation).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

Data waiving (study technically not feasible): Due to the low solubility of the substance (0.2-0.4 mg/L) the study was technically not feasible.

Supporting study: A ready biodegradability manometic respirometry test was performed according to EC C.4 -D and OECD 301F. Test item was incubated for 28 days at a concentration of 100 mg/L (loading rate) with 30 mg/L SS activated sludge inoculum under aerobic conditions in a mineral medium. Additionally, a toxicity test run in parallel (100 mg/L test item with 100 mg/L reference substance and 30 mg/L SS activated sludge inoculum) to check the possible inhibitory effect of the test item. The NOEC (28d) of the substance was determined to be 100 mg/L loading rate since the substance degraded well (83.8% of biodegradation at 28 days) and did not inhibit the degradation in the toxicity test (69.3% of biodegradation after 28 days) up to 100 mg/L loading rate.