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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 - 16 June 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
not specified
GLP compliance:
no
Specific details on test material used for the study:
No further details specified in the study report.
Analytical monitoring:
not specified
Details on sampling:
Concentrations:
Range Finding Study: 10, 100, 1000 mg/l
Definitive Study: 10 mg/l
Vehicle:
no
Details on test solutions:
Method of Preparation: Direct dispersion in water.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Inoculum: A mixed population of activated sewage sludge microorganisms.
Source: The aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
No post exposure observation period specified.
Hardness:
Not specified
Test temperature:
21°C
pH:
pH 7.1
Dissolved oxygen:
Not specified
Salinity:
Not applicable
Conductivity:
Not specified
Nominal and measured concentrations:
Nominal concentrations
Details on test conditions:
The sample was maintained at 21°C with continuous aeration and used on the day of collection. The pH was buffered to pH 7.1 with sodium hydroxide solution and the suspended solids level adjusted to 4.0 g/l prior to use.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 10 - < 100 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):
Reference Material : EC50 (3 hour contact time) = 12 mg/l

Range Finding Study – Date: 15 June 1992

Concentration (mg/l)

O2consumption rates

mg O2/l/min

3 hour contact time

% Inhibition

Control

R1

0.44

-

R2

0.42

-

Test

10

0.43

0

100

0.13

70

1000

0.02

95

Reference

3.2

0.42

2

32

0.06

86

Variation between controls: ± 2%

 

Definitive Study – Date: 16 June 1992

Concentration (mg/l)

O2consumption rate

mg O2/l/min

3 hour contact time

% Inhibition

Control

R1

0.36

-

R2

0.28

-

Test

10

R1

0.28

13

10

R2

0.28

13

10

R3

0.31

3

Reference

3.2

0.28

13

32

0.07

78

R1– R3: Replicates R1– R3

Variation between controls: ±11%

Conclusions:
Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l
Executive summary:

Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l

Description of key information

Key value determined using OECD guideline 209.

Key value for chemical safety assessment

EC50 for microorganisms:
10 mg/L

Additional information

Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l.