Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
3 hours
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test was performed according to OECD test guidelines, and a statement of GLP compliance has been made.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Di-trimethylolpropane
- Lot/batch No.: 93974026
- Purity: 99.4%
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Sampling and analysis

Analytical monitoring:
no
Details on sampling:
Not applicable

Test solutions

Vehicle:
no
Details on test solutions:
A 5 g Di-Trimethylolpropane /L stock solution was prepared by adding Di-Trimethylolpropane (5.0016 g) to a 1000 mL volumetric flask and bringing to volume with deionised water. The solution was ultrasonicated for ca 25 min to aid dissolution.

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
A sample of activated sewage sludge was obtained from Haddington Municipal Sewage Works (a local sewage processing plant, which handles predominantly domestic sewage) on 17 February 2010. On arrival at the laboratory, the sludge was aerated. The solid content of the sludge was determined by shaking the bottle of sludge by hand to homogenise thoroughly. Duplicate sub-samples (5mL) of the homogenised sludge were dried in an oven at approximately 105°C and the suspended solids content determined as 1.6 g/L. To concentrate the solid sewage flocculent to the required level, the sludge was allowed to settle before 4.8 L of the overlying supernant was siphoned off. Synthetic sewage feed was then added at a rate of 50 mL/L sludge. The solid content of the sludge was then re-determined and found to be 4 g/L, which was acceptable for use. The pH of the sludge was measured as 7.54 upon receipt.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Not applicable

Test conditions

Hardness:
Not applicable
Test temperature:
18.9 to 19.5°C
pH:
The pH of the sludge was measured as 7.54 upon receipt.
Dissolved oxygen:
Measured during the study.
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal exposure concentrations were 10, 31.6, 100, 316 and 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
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The 3 h EC50 for 3,5-DCP to activated sludge was estimated to be 11.92 mg/L with 95 % confidence limits of 10.18 and 13.95 mg/L, under the conditions of this test.
Reported statistics and error estimates:
The respiration rate for each vessel was calculated from the recorded oxygen concentrations and expressed as mg O2/L/h for the period between approximately 6.5 and 2.5 mg O2/L. Where respiration was low the calculation was conducted over the full linear range.

The EC50 and associated 95% confidence interval was estimated using the non-parametric Trimmed Spearman-Karber Method (Hamilton et al, 1977), where appropriate.

Any other information on results incl. tables

Respiration rates and percentage inhibition

Treatment

Nominal concentration (mg/L)

Respiration rate
(mg O2/L/h)

% inhibition

Control 1

0

59.04

-

Control 2

0

53.10

-

Mean of controls

-

56.07

-

% difference in controls

-

10.1

-


3,5,-DCP

5

51.30

8.51

15

20.40

63.62

30

11.37

79.72



Di-trimethylolpropane

10

62.16

0

31.6

55.71

0.63

100

60.24

0

316

56.80

0

1000

57.60

0

 

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
As there was no inhibition of respiration at any Di-Trimethylolpropane concentration, the 3 h EC50 for Di-Trimethylolpropane to activated sludge wasestimated as >1000 mg/L, under the conditions of this test.
Executive summary:

The toxicity of Di-Trimethylolpropane to activated sewage sludge was investigated in a respiration inhibition test according to OECD test guideline 209. Following three hours exposure to Di-Trimethylolpropane the EC50 was observed to be > 1000 mg/L (based on nominal exposure concentrations), the corresponding NOEC was observed to be 1000 mg/L.