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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011-05-30 to 2011-07-27
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Name of test material (as cited in study report): Aldehyde C9 Nonylic Food Grade
- Physical state: Liquid
- Lot/batch No.: VE00120901
- Expiration date of the lot/batch: October 14, 2011
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The test substance is not soluble enough in water to allow the preparation of an aqueous stock solution in tap water.

Different stock solutions were prepared by dissolution of Aldehyde C9 Nonylic Food Grade in ethanol in order to add always the same volume (ie 5 ml) of ethanol in each cylinder.

The following solutions were prepared:

A1: solution 100 mg of Aldehyde C9 Nonylic Food Grade in 10 ml ethanol

A2: solution 31.6 mg of Aldehyde C9 Nonylic Food Grade in 10 ml ethanol

A3: solution 10.0 mg of Aldehyde C9 Nonylic Food Grade in 10 ml ethanol

A4: solution 3.2 mg of Aldehyde C9 Nonylic Food Grade in 10 ml ethanol

A5: solution 1.0 mg of Aldehyde C9 Nonylic Food Grade in 10 ml ethanol
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The sludge was kept aerobic until being used on the same day. The pH was between 7 and 8.

The suspended solids content was determined by drying and weighing 50 ml of the sludge: dry weight of suspended solids: 16.76 g/l

By adding 200 ml of sludge to the 500 ml test vessels, the final concentration of suspended solids was 0.88 g/l, ie in the range 0.8 to 1.6 g/l as recommended in ISO 8192-1986
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20 ± 2°C
pH:
Refer to Table 1 test results
Dissolved oxygen:
Refer to Table 1 test results
Nominal and measured concentrations:
1.0, 3.2, 10.0, 31.6 and 100 mg/l
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 ml scaled cylinders
- Aeration: Yes
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
ca. 70 mg/L
Nominal / measured:
nominal
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
31.6 mg/L
Nominal / measured:
nominal
Results with reference substance (positive control):
- Results with reference substance valid? The reference substance showed 3.8 % inhibition at 5 mg/L and 72 % inhibition at 30 mg/L.

Table 1: Test results

vessel

pH

∆O2 [mg/l]

Time [min]

rate

% inhibition

Conc.finale [mg/l]

Log (conc)

C1

8.54

1.90

2.50

0.76

-

-

-

Tr

8.72

2.05

2.50

0.82

-

-

-

R1

8.54

1.90

2.50

0.76

3.8

5.0

0.70

R2

8.56

0.55

5.00

0.22

72.2

30.0

1.48

S1

8.56

0.85

5.00

0.17

78.5

100.0

2.00

S2

8.53

1.95

5.00

0.78

1.3

31.6

1.50

S3

8.45

1.95

5.00

0.78

1.3

10.0

1.00

S4

8.60

1.90

2.50

0.76

3.8

3.2

0.51

S5

8.60

1.95

5.00

0.78

1.3

1.0

0.00

Only at a test concentration of 100 mg/l a significant inhibition of the respiration was observed. For estimating the EC50 (3 hours) a linear relationship between % inhibition and the common logarithm of the test substance concentration was assumed for concentrations ranging from 31.6 mg/l (test vessel S2) to 100 mg/l (test vessel S1). A linear regression was performed (least squares method) and parameters a and b were obtained:

% inhibition = a * log conc. + b

a = 103.269  b = -136.537

Using the equation and parameters above, the concentration corresponding to an inhibition of 50% was calculated EC50 = ~ 0.7 . 102mg/l 

Validity criteria fulfilled:
yes
Conclusions:
The test substance was assessed for activated sludge respiration inhibition according to OECD 209. The EC50 (3 hours) of Aldehyde C9 Nonylic Food Grade is ~ 70 mg/l. The NOEC is 31.6 mg/L.

Description of key information

The test substance was assessed for activated sludge respiration inhibition according to OECD 209. The EC50 (3 hours) of Aldehyde C9 Nonylic Food Grade is ~ 70 mg/l. The NOEC is 31.6mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
70 mg/L
EC10 or NOEC for microorganisms:
31.6 mg/L

Additional information

The test substance was assessed for activated sludge respiration inhibition according to OECD 209. Five concentrations were tested: 1, 3.2, 10, 31.6 and 100mg/L. Only at a test concentration of 100 mg/L was significant inhibition of the respiration observed. Therefore the NOEC is considered to be 31.6 mg/L. For estimating the EC50 (3 hours) a linear relationship between % inhibition and the common logarithm of the test substance concentration was assumed for concentrations ranging from 31.6 to 100mg/l. Using this equation the concentration corresponding to 50% inhibition was calculated to be ~ 70 mg/l.