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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:
other: GLP guideline study with some missing details
Qualifier:
according to guideline
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: direct weighing, the test substance was added to abput 130 ml deionzed water and stirred before testing for 2 hours.
Test organisms (species):
activated sludge of a predominantly industrial sewage
Details on inoculum:
- Preparation of inoculum for exposure: The sludge is settled and supernatant is decanted. After centrifuging (20 min at 4000 rpm and 20°C) the supernatant is decanted again. 1 g of wet sludge is dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 6 g/L (dry wet) suspended solids. The calculated amount of sludge is first dissolved in synthetic medium and then filled up to a defined end volume with deionised water.
- Initial biomass concentration: 6 g/L dw suspended solids
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20°C ± 2 °C
pH:
7.1 - 8.0
Nominal and measured concentrations:
Nominal test concentrations: control, 10, 18, 56, 100 mg a.i./L
Details on test conditions:
TEST SYSTEM
- Biomass loading rate: 6 g/L dw suspended solids

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : respiration inhibition after 3 hours

TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations:
- First range-finding test:100, 1000, 10000 mg/L
- Second range-finding test: 1, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: Since the first range-finding test showed an inhibition greater than 50% at 100 mg/L, a second range-finding test with lower test substance concentrations was conducted. The second test revealed inhibition rates of 0 % and 1.5 % for test substances concentrations of 1 and 10 mg/L, respectively
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
other: EC05
Effect conc.:
26 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
31 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
62.2 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):
EC50 = 9.2 mg/L

Table 1: Respiratory rates, oxygen-consumption and respiration inhibition of the treated activated sludge

Nominal test concentration

[mg a.i./L]

Respiratory rate

[mg/L x h]

Phys.-chem. O2consumption
[mg/L x h]

Respiratory rateminusphys.-chem. O2consumption
[mg/L x h]

Inhibition

[%]

10

18

32

56

100

20

18

19

9.4

3.0

0.0*

0.0*

0.0*

0.0*

0.0*

20

18

19

9.4

3.0

0

0

0

47.6

83.3

Control 1

Control 2

Control, mean

18

18

18

 

 

 

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to analogue justification provided in IUCLID section 13
Reason / purpose for cross-reference:
read-across source
Duration:
3 h
Dose descriptor:
other: EC05
Effect conc.:
26 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
31 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
62.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Description of key information

EC10 (3 h): 31 mg/L (read across)

Key value for chemical safety assessment

EC50 for microorganisms:
62.2 mg/L
EC10 or NOEC for microorganisms:
31 mg/L

Additional information

Reliable data on the toxicity of sodium 2-biphenylate (CAS 132-27-4) to microorganisms are not available. The assessment was therefore based on a study conducted with the analogue substance 2-phenylphenol (CAS 90-43-7) as part of a read across approach, which is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Further justification is given within the overall summary chapter 6.1 and within the analogue justification in IUCLID section 13.

The effect of 2-phenylphenol (CAS 90-43-7) on aquatic micro-organism was investigated according to ISO guideline 8192 comparable with OECD 209 (Mueller, 1990). The study was re-evaluated according to recent regulatory requirements by Weyers (2006). At nominal test concentrations of 10 - 100 mg/L, inhibition of respiration in activated sludge was observed between 0% and 83.3% and a dose - response relationship was demonstrated. An inhibition of microbial activity by 50% was determined at EC50(3 h) = 62.2 mg/L. The EC10(3 h) of 31 mg/L was used for further assessment.

Additional information is available from a study investigating the toxicity of sodium 2-biphenylate toPseudomonas fluorescensandEscherichia coli(Hamburger, 1974). The study followed the modified German Uniform Procedure L8 and determined no adverse effects onE. coliup to 10 g/L and toxic effects onP. fluorescensat concentrations ≥ 1 g/L.