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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-06-16 to 2010-07-09
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 (Carbon and Ammonium Oxidation))
Version / remarks:
Adopted 4th April 1984.
GLP compliance:
yes
Specific details on test material used for the study:
Supplier: Röhm GmbH
Purity: 99.7 %
Batch No. 11100114
Expiry date: 2010-09-08
Analytical monitoring:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Not adapted and not pre-conditioned activated sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant. 1.6 g/l dry matter in the final mixture.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
22 ± 2 °C
Nominal and measured concentrations:
nominal: 31.3, 62.5, 125, 250, 500, 1000 and 2000 mg/I,
Details on test conditions:
Final test concentrations are prepared by directly adding the respective amount of the test substance to the test vessels.
For each test series the following number of test flasks was set up:
- Test suspension (Tn); one replicate sample containing activated sludge + test medium + test substance
- Blank control (B1, B2); two replicate samples containing activated sludge + test medium
- Sensitivity control (Rn); one replicate sample (3 test concentrations) containing activated sludge + test medium + 3,5-dichlorophenol as sensitivity control

The test vessels were aerated by shaking (120 r.p.m.) for the whole test period of 3 hours. The first sample (blank control B1) was analyzed 3 h after starting the test followed by the analysis of the sensitivity controls (Rn) and the test suspensions (Tn) at 5-15 min intervals. Finally, the second blank control B2 was analyzed.
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
37 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
995 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: 95 % confidence limit: 631 - 1995 mg/l
Details on results:
The following respiration inhibition of the activated sludge compared to the two blank controls was observed:
31.3 mg/l (14%), 62.5 mg/l (16%), 125 mg/l (19%), 250 mg/l (30%), 500 mg/l (42%), 1000 mg/l (47%) and 2000 mg/l (65%).

EC20 (3h): 84.3 mg/l
EC80 (3h): > 2000 mg/l
Results with reference substance (positive control):
The EC50 value of the reference substance 3,5-dichlorophenol was estimated to be 4.0 mg/l which was low but in the range of 5 mg/l thus confirming suitability of activated sludge and test conditions. The variation between the two controls was ± 2.3%. Therefore, the test was considered valid

Activated sludge respiration rates after 3 h of exposure to the test material and calculation of the inhibition

Nominal concentration
                       (mg/l)

Code

O2consumption rates
(mg O2
·l-1·h-1)

Respiration inhibition
(%)

Control               0
                          0

B1
B2

             28.3
             30.6

                  -
                  -

                     31.3

T1

             25.4

             13.7

                     62.5

T2

             24.6

             16.4

                      125

T3

             23.8

             19.3

                      250

T4

             20.7

             29.7

                      500

T5

             17.0

             42.3

                    1000

T6

             15.7

             46.5

                    2000

T6

             10.4

             64.6

Reference          3
                        10
                        30

R1
R2
R3

             17.0
               8.2
               3.6

             42.2
             72.3
             87.9

Values in italics were used for linear regression analysis

Validity criteria fulfilled:
yes
Conclusions:
EC50 (3h) was 995 mg/l, EC10 (3h) was 37 mg/l.
Executive summary:

In a vaild respiration inhibition test with activated sludge (OECD 209) Methacrylamide was tested at concentrations of 31.3, 62.5, 125, 250, 500, 1000 and 2000 mg/l (nominal concentrations). EC50 (3h) was 995 mg/l, EC10 (3h) was 37 mg/l.

Description of key information

In a vaild respiration inhibition test with activated sludge (OECD 209) Methacrylamide was tested at concentrations of31.3, 62.5, 125, 250, 500, 1000 and 2000 mg/l (nominal concentrations). EC50 (3h) was 995 mg/l, EC10 (3h) was 37 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
995 mg/L
EC10 or NOEC for microorganisms:
37 mg/L

Additional information