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Diss Factsheets

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1988
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: well performed OECD study but without GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988
Report date:
1988

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
only 4 instead of 5 concentrations, industrial insted of domestic sludge
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
Methyl p-toluate
EC Number:
202-784-1
EC Name:
Methyl p-toluate
Cas Number:
99-75-2
Molecular formula:
C9H10O2
IUPAC Name:
methyl 4-methylbenzoate
Details on test material:
purity: > 99.0 %

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
activated sludge, industrial
Details on inoculum:
Origin: Sewage treatment plant of the Hoechst AG, site Kelsterbach
Type of inoculum: Industrial activated sewage sludge
Preparation of the suspension: sediment from activated sewage sludge was washed three times by centrifuging and resuspending in water with 0.9 % NaCl
Content of suspended solids in the sewage sludge suspension : normally 2 g/L (dry matter) were used
Pre-treatment: corresponding to the cited test guideline, but no detail was recorded in the laboratory test protocol
State of acclimatization : not pre-adapted in the laboratory to the test substance or the reference substance

Study design

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

Test conditions

Test temperature:
22.7 - 23.1 °C
pH:
8.9
Nominal and measured concentrations:
Nominal:
Concentration of the stock solution . : 380 mg DOC/L (analytical value)
According to : 528 mg/L of the substance (calculated from DOC)
Addition of the stock solution : Dilutions 1:2; 1:4, 1:8, and 1:16
Test substance in the batches: 264, 132, 66, and 33 mg/L

Stock solution:
Addition of the test substance: 2000 mg in 1000 ml of de-ionized water
The batch was stirred over 24 hours in a covered beaker at a temperature of about 21°C
The substance sample weighed in was only partly dissolved. The batch was passed through a folded filter. The filtrate was used as stock solution.
The concentration was measured as dissolved carbon content (DOC).
Details on test conditions:
Incubation vessels : Glasbottles with a diameter of 60 mm and a grounded neck (NS 29), height 170 mm and a total volume of approx. 480 ml. The bottles contained magnetic stirrer bars and were incubated in a water bath on magnetic stirrers.
Test volume : 200 ml each batch
Temperature control: laboratory thermostat
Aeration rate/test vessel: normally 45 litres per hour, but the value is not documented in the laboratory manuscript; aeration only during the incubation period
Oxygen measurements : With oxygen electrodes, connected to oximeters and two-channel recorders
Monitoring : During the measuring periods of about 10 minutes without further aeration the oxygen concentration curves were plotted by the recorders
Respiration rate : The slope of the linear part of the respiration curves accorded to the corresponding respiration rates
Measurements of the pH: pH Meters
Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
3 h
Dose descriptor:
other: 0 % respiration inhibition
Effect conc.:
264 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: respiration inhibition
Duration:
3 h
Dose descriptor:
other: 6% respiration inhibition
Effect conc.:
132 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: respiration inhibition
Duration:
3 h
Dose descriptor:
other: 0% respiration inhibition
Effect conc.:
66 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: respiration inhibition
Duration:
3 h
Dose descriptor:
other: 0% respiration inhibition
Effect conc.:
33 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: respiration inhibition

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The EC0 and the EC50 of the substance to industrial activated sludge (Sewage treatment plant of the Hoechst AG, site Kelsterbach) were in the range >100 mg/L to 1000 mg/L.
Executive summary:

The substance was tested for toxicity to bacteria according to OECD guideline 209 in the Respiration Inhibition Test with activated sludge from an industrial waste water treatment plant. The EC0 and EC50 values were found to be in the range 100 - 1000 mg/L.