Phosphoric acid, mono and bis-linear butyl esters, potassium salts

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-02-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Sludge was taken from the activation basin of the ESN (Stadtentsorung Neustadt) sewage treatment plant, Im Altenschemel, 67435 NW-Laken-Speyerdorf
- Pretreatment: The sludge was washed with tap water three times, then centrifuged and re-suspended in tap water. 200 mL of the sludge were added to each test vessel.
- Initial biomass concentration: Dry matter in the test = 1518 mg suspended solids/L.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

not applicable

Hardness:

no data

Test temperature:

20 +/- 2 deg C

pH:

no data

Dissolved oxygen:

no data

Salinity:

no data

Conductivity:

no data

Nominal and measured concentrations:

nominal: 1, 10, 100, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers
- Aeration: yes, approx 0.75 L/min
- No. of vessels per concentration (replicates): 2 for 1000 mg/L, 1 for 1-100 mg/L
- No. of vessels per control (replicates): 2
- No. of vessels per abiotic control (replicates):
- Sludge concentration (weight of dry solids per volume): 1518 mg/L
- Nutrients provided for bacteria: Synthetic sewage
- Biomass loading rate:
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
OTHER TEST CONDITIONS
- Adjustment of pH: no
EFFECT PARAMETERS MEASURED: Respiration rate
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

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

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

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Coefficient of variation of oxygen uptake rate in control replicates: Maximum of 8%, which is below the recommended limit of 15%

Results with reference substance (positive control):

- Results with reference substance valid? yes, EC50 = 5.1 mg/L which is within the recommended range of 5-30 mg/L

Reported statistics and error estimates:

not applicable

The test item showed very little inhibition in the experiment. In the highest treatment (1000 mg/L) no inhibition could be detected. In the the lower treatments, inhibition values stayed below 5%. Therefore, these values were not attributed to an inhibitory effect of the test item.

Validity criteria fulfilled:

yes

Conclusions:

The 3-h EC50 > 1000 mg/L
The 3-h NOEC = 1000 mg/L

Executive summary:

The inhibitory effect of the test item on the respiration rate of activated sludge microorganisms was determined according to OECD TG 209. The test item was tested using 5 concentrations ranging from 1 to 1000 mg/L. Duration of the test was 3 hours. Activated sludge taken from a domestic sewage treatment plant was used as inoculum. After washing, the dry matter was determined as 3.79 g suspended solids/L, giving a concentration of 1.52 g suspended solids/L in the test.

3,5 -dichlorophenol was used as the reference item. Five concentrations were tested; an EC50 of 5.1 was determined, which lies within the range of 5 -30 mg/L.

At 1000 mg/L no inhibition occurred. Therefore the pre-test can be taken as a limit test.

3h NOEC = 1000 mg/L

3h EC50 > 1000 mg/L

Description of key information

3h NOEC = 1000 mg/L

3h EC50 > 1000 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The inhibitory effect of the test item on the respiration rate of activated sludge microorganisms was determined according to OECD TG 209. The test item was tested using 5 concentrations ranging from 1 to 1000 mg/L. Duration of the test was 3 hours. Activated sludge taken from a domestic sewage treatment plant was used as inoculum. After washing, the dry matter was determined as 3.79 g suspended solids/L, giving a concentration of 1.52 g suspended solids/L in the test.

3,5 -dichlorophenol was used as the reference item. Five concentrations were tested; an EC50 of 5.1 was determined, which lies within the range of 5 -30 mg/L.

At 1000 mg/L no inhibition occurred. Therefore the pre-test can be taken as a limit test.

3h NOEC = 1000 mg/L

3h EC50 > 1000 mg/L