Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1999-04-21 to 1999-05-7
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1999
Report Date:
1999

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Specific details on test material used for the study:
- Name of test material (as cited in study report): Jeffcat ZR-50
- Chemical name: 2-propanol, 1-(bis(3-(dimethylamino)propyl)amino)-
- Physical state: liquid
- Analytical purity: 100%
- Lot/batch No.: 184-3-0998
- Expiration date of the lot/batch: not provided
- Storage conditions: room temperature in the dark and dry

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no
Details on test solutions:
- Nominal test concentrations were established in the test mixtures by the addition of appropriate volumes of a stock solution of 0.5 g/L.
- pH of stock solution was measured and adjusted to approximate neutrality before use.
- Test solutions were prepared by additions of dechlorinated tap water, synthetic sewage and microbial inoculum.

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of activated sludge: Oakley Sewage Treatment Works (treats predominantly domestic waste), sample taken the day before the start of the test
- Samples were maintained under aerobic conditions in the lab until the start of testing. Synthetic sewage (50 mL/L) was added and the mixture was aerated overnight.
- MLSS was determined on the day of collection and immediately before the start of the test.
- On the day of the test the MLSS was adjusted to 4 g/L by addition of dechlorinated tap water.
- Initial SS concentration in the test: 1.6 g/L.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
10 min for oxygen consumption rate measurements

Test conditions

Hardness:
190 mg/L (outside range specified in protocol (200-250 mg CaCO3/L), however, this was not considered to affect the results of the test)
Test temperature:
19-21 degrees C
pH:
7.6
Dissolved oxygen:
N/A
Salinity:
N/A
Nominal and measured concentrations:
Nominal: Control, 1.0, 10 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: flask
- Material, size, headspace, fill volume: glass, 500 mL fill volume
- Aeration: yes, during 3 h, using a Pasteur pipette connected to a laboratory supply of oil-free compressed air
- No. of vessels per concentration (replicates): 1 each of 1 and 10 mg/L, 3 of 100 mg/L
- No. of vessels per control (replicates): 1
- After 3 h of exposure, samples were transferred to BOD bottles (capacity 270 mL) and the oxygen consumption rate was measured during 10 min using a Yellow Springs Instruments DO meter, with temperature probe and self-stirring bottle probe, connected to a chart recorder.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated tap water
- Hardness of dilution water: 190 mg CaCO3/L
- Dilution water for preparation of synthetic sewage was softened tap water treated by reverse osmosis and then purified to give resistivity of 18 Megohm/cm
- pH and temperature were measured at the start and end of the test.

OTHER TEST CONDITIONS
- Adjustment of pH: to neutral

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): oxygen consumption rate over 10 min after 3 h of exposure

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol

Results and discussion

Effect concentrationsopen allclose all
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 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.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none
- Effect concentrations exceeding solubility of substance in test medium: none
- Specific respiration rate of control at the end of the test was 106% of the rate established at the start (32.8 mg O2/g/h vs 31.1 mg O2/g/h), showing that the activated sludge was viable.
- Variation in respiration rate in control vials was < 15% (validity criterium).
- No significant differences were observed between exposed samples and control samples.
Results with reference substance (positive control):
3-h EC50 = 10.5 mg/L (95% CI = 8.3-13.5 mg/L), which shows that the activated sludge employed was sensitive to inhibition (acceptable range 5-30 mg/L).
Reported statistics and error estimates:
The 3-h EC50 for DCP and its confidence limits were calculated by the Moving Average Method.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The test substance had no significant inhibitory effect on the respiration rate of the activated sludge at any of the concentrations employed in the test. The 3-h EC50 of the test substance could therefore not be calculated and must be > 100 mg/L, the highest level tested. The 3-h NOEC is consequently >= 100 mg/L. The results of the study can be considered reliable.