Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
from 19 Oct 2009 to 21 Oct 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. Conclusive valid guideline study under GLP conditions.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
swissmedic: Inspection 2007-Nov-05 to 09 and 26 to 30, and 26 to 30-Nov-2007; decision 2008-Apr-30; signature: 2008-Nov-12

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
Name of test material (as cited in study report): Triethyleneglycoldimethylether
Physical state: Liquid
Purity: 99.8% (by GC)
Storage Conditions: In the refrigerator at about 4 °C. Prevent entry of air/oxygen (peroxide formation).

Whereas Monoethyleneglycoldimethylether can be stripped by passing air into aqueous solutions, such stripping was not observed with Diethyleneglycoldimethylether. Therefore stripping of Triethyleneglycoldimethylether is unlikely. This is supported by preliminary analytical measurements for other studies with Triethyleneglycoldimethylether performed at Harlan Laboratories Ltd.
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Sample storage conditions before analysis: none, immediate measurement

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The study was performed with aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf / Switzerland) treating predominantly domestic wastewater. The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.

Based on this ratio, an aliquot of washed sludge was suspended in tap water to obtain a concentration equivalent to 3 g dry material per liter. During the holding period of two days prior to use, the sludge was fed daily with 50 mL synthetic sewage feed* per liter and was kept at room temperature under continuous aeration until use. Before use, the dry weight of the activated sludge was measured again in the inoculum used for the test. The pH of the activated sludge inoculum was adjusted from 8.8 to 7.1 with a diluted sulfuric acid solution.

* Synthetic sewage feed:

16 g peptone
11 g meat extract
3 g urea
0.7 g NaCl
0.4 g CaCl2 × 2H2O
0.2 g MgSO4 × 7H2O
2.8 g K2HPO4
filled up to a final volume of 1 liter with deionized water

At the start of the test, synthetic sewage feed and activated sludge inoculum were added. The inoculum had a sludge concentration of 2.7 g/L dry weight (corresponding to about 1.1 g dry material per liter test medium).

Study design

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

Test conditions

Test temperature:
20°C at the start and 19°C at the end of the incubation period.
pH:
7.4 - 8.4
Dissolved oxygen:
7.9 - 9.0 mg/L
Nominal and measured concentrations:
5000 - 2500 - 1250 - 625 - 310 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type: open
- Material, size, headspace, fill volume: glass, 2000 mL, open, 500 mL
- Aeration: continuously aerated by intense stirring on magnetic stirrers

- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: The inoculum had a sludge concentration of 2.7 g/L dry weight (corresponding to about 1.1 g dry material per liter test medium)


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: local tap water


OTHER TEST CONDITIONS


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Respiration rate (= oxygen consumption rate); measured continually.
For measurement of the respiration rate a well-mixed sample of each test medium was poured into a BOD-flask after three hours incubation time, and was not further aerated. The oxygen consumption rate (in mg O2 L-1 minute-1) was determined from the linear part of the respiration curve in the range 6.5–2.5 mg O2/L. In case of very rapid oxygen consumption, the range used was below the limits indicated above but always within the linear part of the respiration curve. In case of low oxygen consumption the rate was determined over a period of at least ten minutes. During measurement, the samples were continuously stirred on a magnetic stirrer.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: about 2
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol

Results and discussion

Effect concentrationsopen allclose all
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
>= 5 000 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Remarks:
test item
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
>= 5 000 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Remarks:
test item
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
Up to and including the highest test concentration of 5000 mg/L the test item had no significant inhibitory effect (≤10%) on the respiration rate of activated sludge after the incubation period of three hours. Thus, the 3 hour NOEC (EC10) of Triethyleneglycoldimethylether to activated sludge microorganisms was at least 5000 mg/L. This value might even be higher, but concentrations above 5000 mg/L were not tested. The 3 hour EC20, EC50 and EC80 could not be calculated, but were clearly higher than 5000 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid?
yes
The 3 hour EC50 of the reference item 3,5 dichlorophenol (positive control) was calculated to be 14 mg/L (the 95% confidence limits could not be calculated due to mathematical reasons).
- Relevant effect levels:
EC50 between 5 and 30 mg/L
Reported statistics and error estimates:
not require because no effects were observed

Any other information on results incl. tables

The test is regarded as valid since the oxygen consumption rates of the two controls (run at the start and at the end of the test) differed by 3% (guideline-recommendation: the two control respiration rates should be within 15% of each other), and the 3 hour EC50 of the positive control 3,5 dichlorophenol was 14 mg/L (guideline-recommendation: 5–30 mg/L).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Executive summary:

The inhibitory effect of the test item Triethyleneglycoldimethylether on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3 hour respiration inhibition test according to the EU Commission Directive 88/302/EEC, Part C.11, Commission Regulation (EC) No. 440/2008, Part C.11 and the OECD Guideline for Testing of Chemicals, No. 209.

The following nominal concentrations of Triethyleneglycoldimethylether were tested: 310, 625, 1250, 2500 and 5000 mg/L.

In addition, two controls and three different concentrations of the reference item 3,5 dichlorophenol (5, 16 and 50 mg/L) were tested in parallel. The results of these treatments confirmed suitability of the activated sludge and the method used.

Up to and including the highest test concentration of 5000 mg/L the test item had no significant inhibitory effect (≤10%) on the respiration rate of activated sludge after the incubation period of three hours. Thus, the 3 hour NOEC (EC10) of Triethyleneglycoldimethylether to activated sludge microorganisms was at least 5000 mg/L. This value might even be higher, but concentrations above 5000 mg/L were not tested. The 3 hour EC20, EC50 and EC80 could not be calculated, but were clearly higher than 5000 mg/L.