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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1984
GLP compliance:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Test type:
not specified
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Test temperature:
20 °C.
Nominal and measured concentrations:
Nominal: 12, 24, 50, 120, 250 mg/l.
Details on test conditions:
TEST SYSTEM
- Aeration: at constant rate
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): 1 (3 concentrations: 5, 16, 50 mg/l)

EFFECT PARAMETERS MEASURED: respiration rate.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
104 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
ca. 75 mg/L
Nominal / measured:
estimated
Conc. based on:
act. ingr.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
- Results with reference substance valid? yes.
- Relevant effect levels: EC50 = 11 mg/l, after 3-hour exposure.

Contact time: 30 minutes

test concentration DO mg/l DO after 4 min. mg/l respiration rate mg/l.h inhibition %
control 4.1 0.8 50 -
250 6.8 5.6 17 66
120 6.7 5.1 24 53
50 6.0 3.8 32 37
24 4.6 1.9 41 21
12 4.8 1.6 48 6
control 4.9 1.4 52 -

3,5 -dichlorophenol, contact time: 3 hours

test concentration DO mg/l DO after 5 min. mg/l respiration rate mg/l.h inhibition %
control 6.0 2.5 42 -
50 8.3 7.9 5 89
16 8.3 7.0 16 61
5 7.0 4.4 31 26
control 6.0 2.5 42 -
Validity criteria fulfilled:
yes
Conclusions:
Estimated EC50 in terms of respiration rate after 30-minute contact time = 104 mg/l (equivalent to 75 mg/l active ingredient).
Moreover, EC20 > 30 mg/l and EC80 = ca. 400 mg/l.
Executive summary:

Method

OECD guideline 209 (1984). Effect parameter is respiration rate upon 30-minute contact time using activated sludge from a water treatment plant treating mainly domestic sewage.

Results

Estimated EC50 value is 104 mg/l, EC20 > 30 mg/l and EC80 = ca. 400 mg/l. Given a 72 % purity, EC50 = 75 mg/l of active ingredient.

Description of key information

Estimated EC50 = ca. 75 mg/l based on active ingredient.

Key value for chemical safety assessment

EC50 for microorganisms:
75 mg/L

Additional information

Activated sludge, respiration inhibition test, based on OECD guideline 209 (1984).

All tested concentrations (12 -250 mg/l) showed inhibition of the respiration rate, measured as oxygen consumption in mg/l per minute, in aerobic waste water bacteria. Estimated EC50 value was 104 mg/l, equivalent to ca. 75 mg/l of active ingredient.