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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1989
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Qualifier:
equivalent or similar to
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material: not reported
Analytical monitoring:
no
Details on sampling:
not applicable
Vehicle:
no
Details on test solutions:
8 mL of the synthetic medium and 25 mL of activated sludge were added to the dissolved test item. The mixture was filled up to 250 mL with water and aerated at 20°C +/-2°C.
The exposure medium with the reference substance was prepared by adding 8 mL of the sythetic medium, 25 mL of activated sludge and a defined amount of the stock solution to achieve the test concentrations and was filled up to 250 mL with water.
Test organisms (species):
activated sludge
Details on inoculum:
Sludge:
The sludge was withdrawn of a laboratory scale sewage treatment unit (3L).
The start concentration of activated sludge was about 6.00 g/L dry matter. The dry matter content of 1 g of wet activated sludge was 0.03 g. Therefore, a required quantity of 400 g/2 L was used in the test.

Synthetic medium:
A synthetic waste water feed was made by dissolving the following amounts of substance in 1 litre of water:
16.0 g peptone
11.0 g meat extract
3.0 g urea
0.7 g NaCl
0.4 g CaCl2 x 2 H2O
0.2 g MgSO4 x 7 H2O
2.8 g K2HPO4

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
not reported
Hardness:
not reported
Test temperature:
20°C +/- 2°C

pH:
Test 1: 7.5-8.2
Test 2: 7.8-8.5
Dissolved oxygen:
not reported
Salinity:
not reported
Nominal and measured concentrations:
Test 1: nominal concentrations of test item: 100, 1000 and 10000 mg/L
Test 2: nominal concentrations of test item: 1000, 1800, 3200, 5600 and 10000 mg/L
Nominal concentration of reference compound 3.5-Dichlorophenol: 1 and 20 mg/L

Details on test conditions:
not reported
Reference substance (positive control):
yes
Remarks:
3.5-Dichlorophenol was used as reference substance.
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: The test substance showed a respiration inhibition of 48% in test 1 and 31% in test 2 at the highest test itemconcentration of 10000 mg/L.
Details on results:
not reported
Results with reference substance (positive control):
The EC50 of 3.5-Dichlorophenol is in the range 5-30 mg/L.

Reported statistics and error estimates:
not reported

In the following tables the respiration rate, the percentage of inhibition as well as the pH values at the different test concentrations were presented:

Test 1:

 

Test item concentration [mg/L]

Respiration rate

 

[mg/(L*h)]

Inhibition

 

%

pH

Test item

100

28

0

8.1

1000

28

0

8.1

10000

14

48

8.1

Reference substance

1

24

11

8.1

20

6

78

8.2

Control 1

 

27

-

8.1

Control 2

 

27

-

8.1

Test 2:

 

Test item concentration [mg/L]

Respirationrate

 

[mg/(L*h)]

Inhibition

 

%

pH

Test item

1000

36

0

8.5

1800

36

0

8.5

3200

33

6

8.4

5600

30

14

8.4

10000

24

14

8.4

Reference substance

1

33

6

8.3

20

8

77

8.5

Control 1

 

34

-

8.2

Control 2

 

36

-

8.4

 

 

Validity criteria fulfilled:
yes
Remarks:
All validity criteria of the test method were met: - respiratory rates of the 2 controls differ less than 15% - EC50 of 3.5-Dichlorophenol is in the range 5-30 mg/L .
Conclusions:
Vulkanox BKF showed a respiration inhibition of 48% in test 1 and 31% in test 2 at the highest concentration tested, and hence:
EC50 > 10000 mg/L (based on nominal concentrations).
Executive summary:

A respiration inhibition test with activated sludge according to OECD Guideline 209 (1983) was conducted to assess the toxicity of BPH to bacteria. This test method is equal to ISO 8192 "Test for Inhibition of Oxygen Consumption of Activated Sludge".

The respiration rate of each mixture was determined after aeration periods of 3 hours. BPH showed a respiration inhibition of 48% in test 1 and 31% in test 2 at the highest concentration tested, and hence:

EC50 > 10000 mg/L (based on nominal concentrations).

Description of key information

The EC50 (3h) of DBMC for activated sludge was determined to be > 10 000 mg/L. No PNEC can be derived based on this result

Key value for chemical safety assessment

Additional information

A respiration inhibition test with activated sludge according to OECD Guideline 209 (1983) was conducted to assess the toxicity of DBMC to bacteria. This test method is equal to ISO 8192 "Test for Inhibition of Oxygen Consumption of Activated Sludge". The respiration rate of each mixture was determined after aeration periods of 3 hours. DBMC showed a respiration inhibition of 48% in test 1 and 31% in test 2 at the highest concentration tested (10 000 mg/L), and hence: EC50 > 10 000 mg/L (based on nominal concentrations).