Ferrate(1-), [[N,N'-1,2-ethanediylbis[N-[[2-(hydroxy-.kappa.O)phenyl]methyl]glycinato-.kappa.N,.kappa.O]](4-)]-, sodium (1:1), (OC-6-13)-

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:

07-09.12.2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: study conducted acc. to GLP

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The measurement of oxygen content was performed in aliquots of the reaction mixtures after 3-hour exposure period. Bottles with narrow neck and volume of about 280 mL were filled with the sample and positioned on a magnetic stirrer. Then, the oxygen electrode (equipped with a magnetic stirring wheel) was inserted in a way that no air remained in the bottle and that the electrode sealed the bottleneck to avoid contact of the sample with the atmosphere.
The decline of oxygen concentration was measured and recorded in 30-seconds intervals
for 11 minutes.
The pH was determined in the remaining part of the reaction mixture.

Vehicle:

yes

Details on test solutions:

Test substance
The test substance is soluble in deionized water in concentrations needed for the test. The stock solution was prepared by dissolution of 5.0 g of the test substance in 1000 mL deionized water on the day of testing.
The concentrations 10, 100 and three replicates of 1000 mg·L-1 of the test substance were tested in the preliminary test.

Reference substance
The stock solution of the reference substance was prepared by dissolution of 0.1 g
of 3,5-dichlorophenol in 200 mL deionized water. The ultrasound for 60 minutes to accelerate the dissolution was used. The resulting solution has a concentration of 500 mg·L-1 and the pH value of 7 – 8. The stock solution was prepared on the day of testing.
The concentration range used was 5 - 20 mg·L-1. It was calculated by geometric progression with factor of 1.4.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated biological sludge containing mixed culture of microorganisms obtained from the second step of sewage treatment plant of Pardubice was used for the testing. The wastewater processed by the sewage treatment plant is predominantly municipal.

Preparation of the inoculum
The activated sludge was collected two days before the day of testing.
After the sample collection the sludge was washed with potable water for 30 minutes and subsequently decanted for 30 minutes. This procedure was repeated three times in total.
Further the sludge was fed with the 100 mL synthetic sewage feed per 2 L of diluted sludge suspension at permanent aeration till the day of the test.
The suspended solids concentration was determined from 10 mL of sludge suspension after 30-minutes sedimentation.
Before the test the sludge was suspended in water up to concentration about 3000 mg
of suspended solids per litre. The pH adjustment to 6.0 was carried out. In that way modified sludge suspension was aerated until the use.

Justification for the selection of the test system
The activated sludge obtained is in conformity with the recommendations of the test guidelines.

Test type:

static

Water media type:

freshwater

Total exposure duration:

3 h

Test temperature:

20 +/- 2 0C

pH:

7-8

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol, 97%

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

Details on results:

EC values for the test substance, Fe(III)HBED
The highest inhibition the respiration rate of activated sludge caused by the test substance was 10.3 % (see table 4) in the preliminary test. Therefore it was not possible to calculate the EC50 value from the obtained respiration rates.

Results with reference substance (positive control):

1. The difference of two respiration rates of control experiments at the beginning and the end of the main test from each other was:
5.79 % (if the value of lower control 45.60 mg·L-1·h-1 = 100 %)
2. The EC50 value of the reference substance 3,5-dichlorophenol was:
EC50 = 10.1 mg·L-1 (95% confidence interval: 7.4 – 13.9 mg·L-1)

Reported statistics and error estimates:

Calculation of EC values
The values of EC50, EC20 and EC80 for the reference substance were calculated from equation of regression line prepared by commercial software Microsoft® Excel 2013.
The confidence intervals of EC50, EC20 and EC80 for the reference substance were calculated by the software QC.Expert 2.5 © 1998-2000 (product of TriloByte Ltd.. Czech Republic).

Validity criteria fulfilled:

yes

Conclusions:

The highest inhibition the respiration rate of activated sludge caused by the test substance Fe(III)HBED was 10.3 % in the preliminary test. Therefore exact value of EC50 could not be calculated and the value of EC50 is given in the form of a range.

EC50 > 1000 mg·L-1

The low level of inhibition of oxygen consumption by the test substance in the preliminary test demonstrated that a definitive test is unnecessary.

Executive summary:

The influence of the test substance,Fe(III)HBED,on the respirationrate of activated sludge was investigated after a contact time of 3 hours.

 

Test performance

Test was performed according to:

Method C.11 - Activated Sludge Respiration Inhibition Test, Council Regulation (EC)
No. 440/2008, published in O.J.L 142, 2008.

 

The preliminary test was performed using 3 concentrations 10, 100 and 1000 mg·L^-1. Further two blank controls and the three abiotic controls with the highest concentration of the test substance was included.

 

3,5-dichlorophenol was used as reference substance. Five concentrations in geometric progression with a factor of 1.4 (5, 7, 10, 14 and 20 mg·L^-1) were selected.

 

The abiotic decomposition was not detected even at the highest concentration of the test substance.

The pH value during the preliminary test was in the range of 7.3 to 7.8.

 

Validity of the test

The prescribed validity criteria in the test were fulfilled.

Since all criteria of acceptability were met, this study is considered to be valid.

 

Results of the respiration inhibition test

The highest inhibition the respiration rate of the activated sludge caused by the test substanceFe(III)HBEDwas 10.3 % (see table 4) in the preliminary test. Therefore exact value of EC₅₀could not be calculated and the value of EC₅₀is given in the form of a range.

 

EC₅₀> 1000 mg·L^-1

 

The low level of inhibition of oxygen consumption by the test substance in the preliminary test demonstrated that a definitive test is unnecessary.

Description of key information

Fe(III)HBED CAS 1061328-86-6, EC Method C.11, activated sludge: EC50(3h) > 1000 mg/L, 

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

The influence of the test substance,Fe(III)HBED,on the respiration rate of activated sludge was investigated after a contact time of 3 hours (Roupcova, 2015). The test was performed according to EU Method C.11. The preliminary test was performed using 3 concentrations :10, 100 and 1000 mg·L^-1. Further two blank controls and the three abiotic controls with the highest concentration of the test substance were included. 3,5-dichlorophenol was used as reference substance. Five concentrations in geometric progression with a factor of 1.4 (5, 7, 10, 14 and 20 mg·L^-1) were selected. The abiotic decomposition was not detected even at the highest concentration of the test substance. The pH value during the preliminary test was in the range of 7.3 to 7.8. The prescribed validity criteria of the test were fulfilled. Since all criteria of acceptability were met, this study is considered to be valid.

The highest inhibition the respiration rate of the activated sludge caused by the test substance Fe(III)HBED was 10.3 % in the preliminary test. Therefore, an exact value of EC₅₀ could not be calculated and the value of EC₅₀ is given in the form of a range: EC₅₀> 1000 mg·L^-1

The low level of inhibition of oxygen consumption by the test substance in the preliminary test demonstrated that a definitive test is unnecessary.

In summary, EC50 is greater than 1000 mg/L.

The data on the structural analogue Acetic acid, oxo-, sodium salt, reaction products with ethylenediamine and phenol, iron sodium salts (CAS 84539-55-9) could be used to support the result of the key study with the registered substance Fe(III)HBED. The test substance was used in an experiment in accordance to OECD Guideline 209 (BASF SE, 2009). Activated sludge was collected from the aeration tank at a municipal wastewater treatment. Aliquots of the stock solutions with test- or reference substance were pipetted into test vessels and made up with demineralized water to a volume of 150 mL. After that 8 mL synthetic medium were given to the test vessel. To prepare the blank control assays 150 mL of demineralized water and 8 mL synthetic medium were given to the blank control test vessels. The pH-values were measured in all test vessels. An adjustment was not necessary. Demineralized water (42 mL) was added to each test vessel. After addition of 50 mL of the inoculum suspension (dry weight 7.5 g/L) the incubation was started by aeration of the test vessels with pressure air. The vessels for the blank control assays were prepared according to the same procedure without addition of test- or reference item. After 180 minutes incubation the mixtures in the test vessels were placed subsequently into a closed oxygen measuring cell. As results, an EC₅₀(3h), EC₈₀(3h) > 1000 mg/L as well as an EC₁₀(3h): 450 mg/L is reported.