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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
31 July - 1 August 1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
The study generally follows test guideline OECD209. The test report is without detailed documentation. The test parameters documented do not totally comply with the specific testing guideline, but are sufficient to accept the data.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
Guideline followed not mentioned on the study report
GLP compliance:
not specified
Specific details on test material used for the study:
Dark straw coloured liquid
Storage: in original container at room temperature
Vehicle:
no
Details on test solutions:
Method of prepartion: Direct dispersion in water
Test organisms (species):
activated sludge
Details on inoculum:
A mixed population of activated sewage sludge microorganisms.
Source: The aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire, UK
Test type:
not specified
Water media type:
not specified
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
21 °C
pH:
7.0
Nominal and measured concentrations:
100 mg/l nominal
Details on test conditions:
TEST SYSTEM
- Aeration: continous
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 3.9 g/l

OTHER TEST CONDITIONS
- Adjustment of pH: addition of sodium hydroxide solution

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
O2 consumption mgO2/l/min

TEST CONCENTRATIONS
- Range finding study:
- Test concentrations: 0.1, 10, 100, 1000 mg/l
- Results used to determine the conditions for the definitive study: % inhibition 100mg/l: 6%, %inhibition 1000 mg/l: 92%
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol, concentrations: 3.2 and 32 mg/l
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
not specified
Basis for effect:
inhibition of total respiration
Remarks:
measured O2 consumption rates mgO2/l/min
Results with reference substance (positive control):
Concentration 3.2 mg/l: 15% inhibition
Concentration 32 mg/l: 87% inhibition
Variation between controls: +/- 2%

 Concentration

(mg/l)

 O2 consumption rates

mgO2/l/min

3 hour contact time

 % inhibition

 Control R1

R2

0.44

0.45

 -

-

Test 100 R1

100 R2

  100 R3

0.44

0.42

0.40

1

6

10

Reference 3.2

Reference 32

 0.38

0.06

 15

87

Conclusions:
The EC50 (3 hour contact time) of the test material is >100 mg/l.

Description of key information

The EC50 (3 hour contact time) of the test material is >100 mg/l.

Key value for chemical safety assessment

Additional information