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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1999-08-13
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
Exposure time was reduced from 3 hours to 30 minutes.
Qualifier:
according to guideline
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
- Name of the test material used in the study report: Dimethylolpropionsäure, 2,2-Bis(hydroxymethyl)propionsäure
- Batch no.: SE 8069
- Purity: 99.4%
Analytical monitoring:
no
Details on sampling:
Not applicable
Vehicle:
no
Test organisms (species):
activated sludge
Details on inoculum:
Activated sludge was taken from laboratory wastewater plants treating municipal sewage.

The inoculum was washed, brought to a concentration of 5 g/I dry substance and aerated for about 24 hours. 50 ml were added to a total volume of 250 ml to obtain a concentration of 1 g/I dry substance in the test.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
30 min
Post exposure observation period:
Not applicable
Hardness:
Not applicable
Test temperature:
20 ± 2 °C
pH:
See results tables
Dissolved oxygen:
See results tables
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentration of dimethylolpropionsaure used: 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
other: EC20
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
30 min
Dose descriptor:
other: EC80
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
Not applicable
Results with reference substance (positive control):
Reference substance after 30 min incubation time:
 
EC20(mg/L) - 1.5
EC50(mg/L) - 5.5
EC80(mg/L) - 45

 
 
Reported statistics and error estimates:
Not applicable

pH values during the study



























Vessel number



BC1



BC2



BC3



TS1



pH value before adding the inoculum:
before correction:
after correction:




6.7
7.2




6.7
7.2




6.7
7.4




6.8
7.2



pH value after 30 minute incubation



-



-



-



7.5



 


 


Results of the definitive test after 30 min incubation period with 1000 mg/L dimethylolpropionsaure






























































Vessel no.



mv BC



TS1



RS1



RS2



RS3



Oxygen concentration start (mg O2/L)



-



7.8



7.4



8.2



8.7



Oxygen concentration after 6 min (mg O2/L)



-



5.8



5.7



7.5



8.5



Oxygen consumption rate (mg O2/L x 6 min)



1.9



2.0



1.7



0.7



0.2



Oxygen consumption rate (mg O2/L x h)



19



20



17



7



2



Specific oxygen consumption rate (mg O2/g x h)



19



20



17



7



2



Change in oxygen consumption rate compared with the blank control (%)



-



-5



11



63



89



mv BC = mean value of blank control


TS = test substance


RS = reference number


 


 


Reference substance after 30 min incubation time




















 



EC20(mg/L)



EC50(mg/L)



EC80(mg/L)



Highest concentration tested (mg/L)



Reference substance



ca. 1.5



ca. 5.5



ca. 45



100



 

Validity criteria fulfilled:
yes
Remarks:
The EC50 for the reference inhibitor, 3,5-dichlorophenol was in the range of 5 - 30 mg/L.
Conclusions:
The 30-minute EC50 based on respiration inhibition was >1000 mg/L (the highest nominal exposure concentration tested).
Executive summary:

In a 30-minute toxicity study, inoculum (taken from municipal waster water treatment plant activated sludge) was exposed to Bis-MPA at the nominal concentration of 1000 mg/L in accordance with the OECD 209 guideline. The EC20, EC50, EC80 values for respiration inhibition were >1000 mg/L.


This study is classified as acceptable and satisfies the guideline requirements for an activated sludge respiration inhibition test.

Description of key information

A short-term toxicity test with activated sludge inoculum resulted in an EC20/EC50 for respiration inhibition of >1000 mg/L.

Key value for chemical safety assessment

Additional information

In an activated sludge respiration inhibition according to OECD test guideline 209 Bis-MPA did not impair the respiration rate of the test inoculum at a concentrations of 1000 mg/L. Therefore, no hazard to microorganisms associated with Bis-MPA has been identified.