Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands, receiving predominantly domestic sewage.
The sludge was coarsely sieved, washed and diluted with ISO-medium. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (4.3 g/I of sludge, as used for the test). The pH was 7.8 on the day of sampling and 7.5 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
18-18.6 degrees C
pH:
7.9
Dissolved oxygen:
7.7-7.8 mg/L
Nominal and measured concentrations:
100 mg/L test material nominal (88 mg/L active substance nominal).
Details on test conditions:
Type: other: Activated sludge respiration inhibition test
TEST SYSTEM
- Test vessel: All glass, approximately 300 ml oxygen bottles and 1 litre test bottles.


TEST MEDIUM / WATER PARAMETERS
Adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with the following composition:
CaCI2.2H2O 211.5 mg/I
MgSO4.7H2O 88.8 mg/I
NaHCO3 46.7 mg/I
KCl 4.2 mg/I

SYNTHETIC SEWAGE FEED
16 g peptone 11 g meat extract
3 gurea
0.7 g NaCI
0.4 g CaCI2.2H2O
0.2 g MgS04.7H2O
2.8 g K2HP04
Dissolved in Milli-Q water, made up to 1 litre and filtered.
The pH was adjusted from 6.8 to 7.0 with 1 M NaOH (Merck, Darmstadt, Germany).

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Oxygen consumption

TEST CONCENTRATIONS
Limit test
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 88.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: corrected for lactic acid content of the test material (88.2 %)
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
>= 88.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: corrected for lactic acid content of the test material (88.2 %)
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50 5.9 mg/L
Validity criteria fulfilled:
yes
Conclusions:
Lactic acid 88.2% does not inhibit activated sludge respiration at concentrations up to 100 mg/L test material (88.2 mg/L active substance). Inhibition was -1.1% (stimulation).
Executive summary:

The influence of lactic acid on the respiration rate of activated sludge was investigated after a contact time of 3 hours.

The study procedure was based on OECD guideline 209 (adopted April 4, 1984), EEC Directive 67/548 amended November 18, 1987 (87/302), Part C, Publication No. L133, adopted May 30, 1988 and ISO Standard 8192 (1986).

The batch of the test material was a clear and colourless liquid (88.2 % aqueous solution of lactic acid) that could easily be mixed with water. A stock solution of 500 mg/L was prepared by adding 126.0 mg test substance to 250 ml of Milli-RO water. A stirring period of 30 minutes was used to accelerate dissolution and to ensure homogeneity. Volumes of the stock solution corresponding to the test concentration were then added to the test media. A concentration of 100 mg/L of the test material was tested in duplicate. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring.

No significant inhibition of the respiration rate of the sludge was recorded at 100 mg test material per litre. The duplicate measurement confirmed the result of the first measurement. Therefore no further testing was needed.

Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, under the conditions of this present test, lactic acid was not toxic to waste water (activated sludge) bacteria at a concentration of 88.2 mg/L (corrected for lactic acid content of the test material).

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

A NOEC of 88.2 mg/L (lactic acid, 3 h) was determined with the parameter of total respiration inhibition, in accordance with the OECD guideline 209.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
88.2 mg/L

Additional information