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Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008-11-24 to 2008-11-26
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: See "Principles of method if other than guideline"

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report date:
2008

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
At least five concentrations, spaced by a constant factor preferably not exceeding 3.2, should be used according to the guidelines.
Opposed to that, three concentration were used only (10; 100; and 1000 mg/L).
No analytical monitoring was performed.
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
2-phosphonobutane-1,2,4-tricarboxylic acid
EC Number:
253-733-5
EC Name:
2-phosphonobutane-1,2,4-tricarboxylic acid
Cas Number:
37971-36-1
Molecular formula:
C7H11O9P
IUPAC Name:
2-phosphonobutane-1,2,4-tricarboxylic acid
Details on test material:
- Name of test material (as cited in study report): 2-Phosphono-1,2,4-butanetricarboxylic acid
- Lot/batch No.: CH3/30098
-50.4% active ingredient (a.i.)

Sampling and analysis

Analytical monitoring:
no

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Origin: aeration tank of a domestic sewage treatment plant (Municipal STP Cologne-Stammheim)

Laboratory culture:Date of collection: 2008-11-24

Microbial inoculum:
- first, the sludge was settled and the supernatant was decanted
- after centrifuging (15 min at 4000 rpm and 20°C) the supernatant was decanted
- approx. 1 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry weight) suspended solids
- the calculated amount of sludge was first dissolved in synthetic medium and than filled up to a defined end volume with deionised water - before start of the test 10 mL of the sludge suspension were sucked of and the dry weight was controlled again. The sludge suspension was diluted with water to obtain a concentration of activated sludge of 2 g/L (dry weight) suspended solids

Storage of sludge: aeration of the activated sludge at 20°C ± 2°C, daily fed with synthetic medium

pH of the suspension before application: 7.7

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h

Test conditions

Test temperature:
Test item: 18.5 - 18.7 °C
pH:
Test item: 8.0 - 8.1
Dissolved oxygen:
Start: 6.2 - 6.4 mg O2/L
End: 2.8 - 3.7 mg/L
Nominal and measured concentrations:
Nominal: 10; 100; 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3.5-Dichlorophenol

Results and discussion

Effect concentrationsopen allclose all
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Remarks on result:
other: Bayhibit AM showed 4.3 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L.
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Remarks on result:
other: Bayhibit AM showed 4.3 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L.
Results with reference substance (positive control):
The results with 3.5-Dichlorophenol:
15% inhibition and 18.0 mg/L*h at a concentration of 5 mg/L.
59.1% inhibition and 8.7 mg/L*h at a concentration of 10 mg/L.
83.8% inhibition and 3.4 mg/L*h at a concentration of 20 mg/L.
Reported statistics and error estimates:
probit analysis

Any other information on results incl. tables

Table: Results of test item Bayhibit AM

Test item concentration (nominal)

[mg/L]

Respiratory rate test item

[mg/L*h]

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

Respiratory rate - phys.-chem. O2consumption [mg/L*h]

Inhibition

[%]

10

23.3

0.0*

23.3

0.0

100

22.7

0.0*

22.7

0.0

1000

20.3

0.0

20.3

4.3

* The physico-chemical oxygen consumption has been determined at 1000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Executive summary:

A study was performed to assess the toxicity of Bayhibit AM to microorganisms. The study was conducted in accordance with Council Regulation (EC) No 440/2008, Method C.11 "Activated sludge respiration inhibition" (2008). This test method is equal to OECD Guideline 209 (1984). The activated sludge was exposed to a 50.4% water solution of Bayhibit AM at different concentrations. The respiration rate of each mixture was determined after aeration periods of 3 hours. Bayhibit AM showed 4.3 % respiration inhibition of activated sludge at a test item concentration of 1000 mg/L. The EC50 is higher than 1000 mg/L. The effect value related to nominal concentration, since no analytical monitoring was performed.

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