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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994-04-15
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
GLP study according to OECD 209 (1984): only one concentration was tested, which corresponds to the highest test concentration that could be prepared due to the limited solubility of the test material in water
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
(1984)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
singed 1994-03-16
Analytical monitoring:
no
Details on sampling:
not applicable
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Direct dispersion in water
- Differential loading: No, 100 mg test item/L tested in triplicate
- Controls: yes, one control in duplicate
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Method of cultivation: None, direct use on the day of collection
- Preparation of inoculum for exposure: 16 mL of synthetic sewage and 250 mL of the 200 mg/L stock solution were dispersed in a 500 mL conical flask. The volume was then made up to 300 mL and 200 mL inoculum were added.
- Pretreatment: THe pH was equal to 7.1 and the suspended solids equal to 3.7 g/L, continuous aeration
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Hardness:
dilution water: 100 mg/L as CaCO3
Test temperature:
21 °C
pH:
7.1
Dissolved oxygen:
no data; continuous aeration
Nominal and measured concentrations:
Nominal concentration: 0 (control), 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 mL conical flask filled with 300 mL
- Aeration: continuous aeration
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 2
- No. of vessels per abiotic control (replicates):
- Sludge concentration: 3.7 g/L
- Nutrients provided for bacteria: synthetic waste water according to OECD 209

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated tap water was used; synthetic sewage (according to OECD 209) was added to the activated sewage

OTHER TEST CONDITIONS
- Photoperiod: normal laboratory light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
The rate of respiration for each culture was measured for a 10-minute period after 30 minutes and 3 hours contact time.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not applicable, limit test
- Justification for using fewer concentrations than requested by guideline: limit test with the highest test concentration that could be prepared due to the limited solubility of the test material in water.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: EC50 of 8.0 mg/L (3 h)
Reported statistics and error estimates:
The percentage inhibition was plotted against the concentration and the EC50 values were derived by inspection for 30 minutes and 3 hours contact time.

Oxygen consumption rates and percentage inhibition values

 

Concentration

(mg/L)

02consumption rates

(mg 02/L/min)

% inhibition

 

 

 

 

30 minutes

 

Control R1

             R2

0.47

0.46

-

-

Test item

100 R1

100 R2

100 R3

 

0.40

0.40

0.37

 

14

14

20

3,5-dichlorophenol

3.2

10

32

 

0.43

0.23

0.09

 

8

51

51

 

 

 

 

3 hours

Control R1

             R2

0.42

0.38

-

-

Test item

100 R1

100 R2

100 R3

 

0.35

0.33

0.32

 

13

18

20

3,5-dichlorophenol

3.2

10

32

 

0.33

0.14

0.06

 

18

65

85

R1and R3= Replicates 1 – 3.

Validity criteria fulfilled:
yes
Conclusions:
The substance showed an inhibition of 16.7 % ± 3.6 % at a test item concentration of 100 mg/L after 3 hours, which corresponds to the highest test concentration that could be prepared due to the limited solubility of the test material in water. The 3-hour EC50 value for inhibition of respiration was therefore determined to be >100 mg/L.
Executive summary:

The inhibition of respiration of activated sewage sludge by the test item was investigated in a 3-hour static test under GLP according to OECD 209 (1984). The substance showed an inhibition of 16.7 % ± 3.6 % at a test item concentration of 100 mg/L after 3 hours, which corresponds to the highest test concentration that could be prepared due to the limited solubility of the test material in water. The 3-hour EC50 value for inhibition of respiration was therefore determined to be >100 mg/L.

Description of key information

The 3-hour EC50 value for inhibition of activated sludge was estimated with >100 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

The inhibition of respiration of activated sewage sludge by the test item was investigated in a 3-hour static test under GLP according to OECD 209 (1984). The substance showed an inhibition of 16.7 % ± 3.6 % at a test item concentration of 100 mg/L after 3 hours, which corresponds to the highest test concentration that could be prepared due to the limited solubility of the test material in water. The 3-hour EC50 value for inhibition of respiration was therefore determined to be >100 mg/L.