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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
other: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From August 12, 1993 to August 18, 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
preparation of the inoculum: higher sludge weight after the washing procedure (sludge concentration in the test according to the guidelines); 4 instead of 5 test conc.
Principles of method if other than guideline:
SAV: 05 000 02
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Details on sampling:
No data
Vehicle:
yes
Details on test solutions:
Since the test substance swam at the surface of the medium, the stock solution was prepared by adding one drop of the emulsifier Tween 80 (concentration 35.2 mg/L). The highest solvent concentration used in the test (22.53 mg/L) was additionally tested as solvent control.
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Activated sludge from ARA Pro Rheno Basel (communal sewage treatment plant).
Pretreated by washing 3 times with tap water and addition of synthetic sewage (one day before main test).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Remarks on exposure duration:
None
Post exposure observation period:
No data
Hardness:
No data
Test temperature:
20.9 °C

pH:
7.9-8.1
Dissolved oxygen:
No data
Salinity:
No data
Nominal and measured concentrations:
Nominal concentrations: 0, 10, 32, 100 and 320 mg/L

Details on test conditions:
Sludge dry weight: 1.5 g/L
Test volume: 100 mL
Estimation technique: O2-consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530 (SAV: 00 109)
Aeration: 0.1 - 0.2 L/min by pasteur-pipette
pH of sludge: 7.6 before the test beginning


Reference substance (positive control):
yes
Remarks:
(3,5-dichlorophenol)
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 320 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
- Results with reference substance valid
- Relevant effect levels: 3h IC50 = 13.5 mg/L

Results:

Control

pH

after

3h

1)

O2-consumption

(in cm)

2) time

(in cm)

mg O2 / min/L

Legend:

C =Control;

1) 2 cm=0.8 mg/L O2;

2) 2 cm= 1 minute

C1

C2

8.1

8.0

4.6

4.5

3.7

3.8

0.99

0.95

ΦC 0.97

C1/C2 : 4.21%

C2/C2 : 4.04%

 

Test substance(mg/L)

pH

after

3h

1)

O2-consumption

(in cm)

2) time

(in cm)

mg O2

pro minute/L

%

of control

%

inhibition

320

7.9

4.9

4.1

0.96

98.97

1.03

100

8.0

4.7

4.0

0.94

96.91

3.09

32

8.0

4.8

4.1

0.94

96.91

3.09

10

8.1

4.5

3.8

0.95

97.94

2.06

 

3,5-

Dichlorophenol

(mg/L)

pH

after

3h

1)

O2-consumption

(in cm)

2) time

(in cm)

mg 0 2

pro minute/L

%

of control

%

inhibition

32

8.2

1.2

5.6

0.17

17.53

82.47

10

8.1

3.7

5.0

0.59

80.82

39.18

3.2

8.1

4.4

4.2

0.84

86.60

13.40

Validity criteria fulfilled:
yes
Conclusions:
Under the test conditions, the IC50 of the test substance was determined to be > 320 mg/L (i.e. > 290 mg a.i./L). The 3 h IC50 for the reference substance was 13.5 mg/L.


Executive summary:

A study was conducted to determine the toxicity of the test substance to activated sludge according to OECD Guideline 209 in compliance with GLP.

Sludge from a domestic wastewater treatment plant was exposed for 3 h at 0, 10, 32, 100 and 320 mg/L. The reference substance 3 -5, dichlorophenol was also tested at 3.2, 10 and 32 mg/l.

Under the study conditions, the 3 h IC50 was > 320 mg/L (i.e. > 290 mg a.i./L). The 3 h IC50 for the reference substance was 13.5 mg/L.

Description of key information

IC50(3h) > 320 mg/L (i.e. > 290 mg a.i./L)

Key value for chemical safety assessment

EC50 for microorganisms:
290 mg/L

Additional information