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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Mai - July 1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to
Guideline:
other: 88/302/EWG (Teil C), EG Amtsblatt L 133
Version / remarks:
1988, S. 118 - 122 "Belebtschlamm: Prüfung der Atmungshemmung"
Deviations:
no
GLP compliance:
yes
Test material information:
Composition 1
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The test item was solved in water and stirred for 2 hours at 24.2 °C. The pH was addapted from 1.4 to 7.0.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Name and location of sewage treatment plant where inoculum was collected: Frankfurt - Sindlingen
- Preparation of inoculum for exposure: following the EG Guideline
- Pretreatment: no
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20 ± 2°C
pH:
7.2 + 0.2
Nominal and measured concentrations:
Nominal concentrations: 500 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: bottles with Schliff NS 29 in water bath
- Material, size, headspace, fill volume: glass, diameter 60mm hight 170 mm volume 480 mL
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 3
- No. of vessels per positive control (replicates): 1

OTHER TEST CONDITIONS
- Adjustment of pH: yes

EFFECT PARAMETERS MEASURED:
respiration inhibition with Oximeter (WTW Oxi 537)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: not specified
Reference substance (positive control):
yes
Remarks:
Dichlorphenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
EC100
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
- Any observations that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no
- Adsorption: no
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: EC50 between 5 and 20 mg/L

[mg/L]

Activity [mg O2/L*h]

Inhibition [%]

Mean

Control (Rep. 1)

43.5

-

43.0

Control (Rep. 2)

45.0

-

Control (Rep. 3)

40.5

-

DCP 5

28.5

33.7

-

DCP 20

12.0

72.1

-

DCP 30

10.5

75.6

-

1000 (Rep. 1)

39.0

9.3

7.6

1000 (Rep. 2)

40.5

5.8

500 (Rep. 1)

43.5

-1.2

-1.2

500 (Rep. 2)

43.5

-1.2

DCP: Dichlorphenol

Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC100 and EC50 values were determined to be above 1000 mg/L. Based on the statistical and biological evaluation in this test the NOEC was determined as 1000 mg/L.
Executive summary:

The purpose of the 3-hour test was to evaluate the influence of the test item on the activity of activated sludge by measuring the respiration rate under defined conditions. The respiration rates of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours. The test item was investigated at the nominal concentrations of 500 and 1000 mg/L, with pH adjustment. Defined amounts of the test item were added directly into the test vessels. Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC50 value of test item was determined above 1000 mg/L. Based on the statistical and biological evaluation in this test the NOEC was determined to be 1000 mg/L.

Description of key information

Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC100 and EC50 values were determined to be above 1000 mg/L. Based on the statistical and biological evaluation in this test the NOEC was determined as 1000 mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The purpose of the 3-hour test was to evaluate the influence of the test item on the activity of activated sludge by measuring the respiration rate under defined conditions. The respiration rates of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours. The test item was investigated at the nominal concentrations of 500 and 1000 mg/L, with pH adjustment. Defined amounts of the test item were added directly into the test vessels. Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC50 value of test item was determined above 1000 mg/L. Based on the statistical and biological evaluation in this test the NOEC was determined to be 1000 mg/L.

Two additional studies (with very limited documentation) are available which were conducted to investigate the toxicity of the test material to bacteria for 24-h under anaerobic conditions. As a result, the EC0 and EC50 values of the test item were found to be 1250 and >5000 mg/L, respectively, thus, supporting the above mentioned results.