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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
01 December, 1993 to 14 December, 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
(Deionised water instead of distilled water used for preparation of stock solution; preparation of the inoculum: higher sludge weight after the washing procedure (sludge concentration in the test according to the guidelines); 4 instead of 5 test conc)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Test material: FAT 36034/E
Batch No.: 9300102
Expiry date: July, 1998
Purity: 93 %
Solubility: in water <0.1 g/L
Colour: red
Storage: at room temperature
Analytical monitoring:
yes
Vehicle:
yes
Details on test solutions:
Stock solution: The concentration of the stock "solution" is 0.5 g/L. It was prepared using a 10 minutes ultrasonic treatment for homogenization.
Test organisms (species):
activated sludge
Details on inoculum:
Organism: Activated sludge of a communal sewage treatment plant (ARA-Birsig Therwil)
Sludge pretreatment: 3 times washing with tap water and addition of synthetic sewage (a day before the main test)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21 ⁰C
pH:
7.7-7.9
Nominal and measured concentrations:
Nominal concentrations: 10, 32, 100 and 320 mg/L
Details on test conditions:
Sludge dry weight: 1.44 g/L
Test volume: 100 mL
Estimation technique: O2-consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530 (SAV: 00 109)
Aeration: 0.1 - 0.2 L/min by Pasteur-pipette
pH of sludge: 7.8 before the test beginning
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 320 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:
IC50
Effect conc.:
> 314 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The % inhibitions observed at 0, 0, 0.57 and 0 % at 10, 32, 100 and 320 mg/L, respectively.
Results with reference substance (positive control):
The IC50 (3 h) of the reference substance 3,5-Dichlorophenol: 13 mg/L.

Results:


 






















Control



pH


after


3h



1)


O2-consumption


(in cm)



2) time


(in cm)



mg O2 / min/L



Legend:


C =Control;


1) 2 cm=0.8 mg/L O2;


2) 2 cm= 1 minute



C1


C2



8.0


7.7



4.3


4.4



3.8


4.2



0.91


0.84



ΦC 0.875


C1/C2: 8.33 %


C2/C2: 7.69 %



 



















































Test substance(mg/L)



pH


after


3h



1)


O2-consumption


(in cm)



2) time


(in cm)



mg 0 2


pro minute/L



%


of control



%


inhibition



320



7.7



4.9



4.3



0.91



104.00



0.00



100



7.9



4.7



4.3



0.87



99.43



0.57



32



7.8



5.3



4.7



0.90



102.86



0.00



10



7.8



4.4



4.0



0.88



100.57



0.00



 










































3,5-


Dichlorophenol


(mg/L)



pH


after


3h



1)


O2-consumption


(in cm)



2) time


(in cm)



mg 0 2


pro minute/L



%


of control



%


inhibition



32



7.9



1.0



5.9



0.14



16.00



84.00



10



7.7



3.0



4.6



0.52



59.43



40.57



3.2



7.7



4.0



4.1



0.78



89.14



10.86


Validity criteria fulfilled:
yes
Conclusions:
The IC50 of the test substance was determined to be > 320 mg/L (i.e. > 298 mg a.i./L).
Executive summary:

A study was conducted to assess the inhibitory effect of the test substance (of ca. 93 % purity) on the oxygen consumption rate of aerobic microorganisms (activated sludge) according to OECD Guideline 209 in compliance with GLP.


 


Activated sludge of a communal sewage treatment plant was exposed to the test substance (10, 32, 100 and 320 mg/L) for 3 h and analyzed for oxygen consumption rate. The % inhibitions observed at 0, 0, 0.57 and 0 % at 10, 32, 100 and 320 mg/L, respectively. Hence, the IC50 of the test substance was determined to be >320 mg/L (i.e. >298 mg a.i./L).

Description of key information

A study was conducted to assess the inhibitory effect of the test substance (of ca. 93 % purity) on the oxygen consumption rate of aerobic microorganisms (activated sludge) according to OECD Guideline 209 in compliance with GLP. Activated sludge of a communal sewage treatment plant was exposed to the test substance (10, 32, 100 and 320 mg/L) for 3 h and analyzed for oxygen consumption rate. 3,5-dichlorophenol was used as reference material. Under the test conditions, the IC50 of the test substance was determined to be > 320 mg/L (i.e. > 298 mg a.i./L).


This outcome was further supported in studies with FAT 36034/A and FAT 36034/B, where the IC50 was observed to be >300 mg/L (nominal; test material).

Key value for chemical safety assessment

EC50 for microorganisms:
320 mg/L

Additional information