Tar bases, coal, lutidine fraction

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-03-16 until 2016-04-13

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage treatment plant Ruhrverband Kläranlage, Sunthelle 6, 57392 Schmallenberg, Germany
- Date of sampling: 16th March 2016
- Storage conditions: No storage
- Preparation of inoculum for exposure: No washing, the concentration was adjusted to 3.5 g/L and verified by dry mass
measurement.
- Pretreatment: Kept aerobic until use
- Concentration of sludge in the test: 29.5 mg dry mass/litre

Duration of test (contact time):

28 d

Initial conc.:

28 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

(87.0 mg ThOD considering total nitrification and 69.9 mg ThOD considering the total lack of nitrification.)

Details on study design:

- The concentration in the test assays were 28 mg per litre mineral test medium (7 mg/250 mL). 28 mg test item correspond to 87.0 mg ThOD considering total nitrification and 69.9 mg ThOD considering the total lack of nitrification. The required amount of test item was added as a stock solution. Subsequently, the required volume of aqueous reference stock solution and
mineral medium were added to the vessels.
- The concentration in the test vessels with reference item (procedural control, toxicity control) was 100 mg per litre mineral test
mediummedium (25 mg/250 mL).
- A further solution containing both test and reference item at the same concentrations as in the individual solutions (test item 28
mg/L, reference item 100 mg/L) was prepared to determine the possible toxicity of the test item against the inoculum.
- Further flasks with mineral medium only were prepared for inoculum controls.
- Abiotic controls were also prepared to measure any possible abiotic degradation; a solution of the test item at about 28 mg/L was
sterilized by the addition of 1 mL/L HgCl2 (10 g/L).
- In all test assays except of the abiotic controls, 2.13 mL of the inoculum stock solution were transferred for inoculation (per 250 mL)
resulting in a concentration of 29.5 mg dry mass/litre (7.4 mg dry mass/250 mL).

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

0

St. dev.:

7.1

Sampling time:

28 d

Details on results:

No biodegradation of the test item CA3490A in the test media could be calculated since less oxygen was consumed in the test media than in the blank inoculum and a standard deviation of 7.1% based on ThODNH3 and 5.7% based on ThOD NO3 were respectively observed after 28 days of incubation. No biodegradation within the 10-day-window could be calculated since the start criterion of the window (10% degradation rate) was not reached within the 28 days of incubation.

Results with reference substance:

The reference item was degraded by an average of 83% by Exposure Day 14, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 87%.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The biochemical oxygen demand (BOD) of the test item in the test media was in the range of the inoculum controls throughout the study period of 28 days. Consequently, the test item was not biodegradable under the test conditions within 28 days.

Executive summary:

The ready biodegradability of the test item was investigated according to the manometric respirometry test design and carried out according to the OECD guideline for Testing of Chemicals No. 301 F (1992) and the Council Regulation (EC) No 440/2008 of 30 May 2008. The experiment is considered relevant, adequate and conclusive.

The ready biodegradability of the test item was investigated at a concentration of 28 mg/L in a manometric respirometry test using domestic aerobic activated sewage sludge incubated at 22 °C in the dark over 28 days under continuous stirring. The biochemical oxygen demand (BOD) was measured daily and the percentage degradation was calculated from the theoretical oxygen demand (ThOD) after correcting for the BOD of inoculum controls. The biochemical oxygen demand of the test item in the test media was in the same range as the inoculum controls, so the test item exhibited no significant additional oxygen demand. Consequently, the test item was not biodegradable under the conditions of the test. The test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration. In the procedural controls, the reference substance sodium benzoate was degraded by an average of 83% by exposure day 14, and reached an average biodegradation of 87% by the end of the test (day 28), thus confirming suitability of the activated sludge.

Description of key information

OECD 301F: the substance was not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready biodegradability of the substance was investigated under GLP in a standard Manometric Respirometry Test according to OECD Guideline 301 F. No significant biodegradation was observed in this study, and the substance was considered as not readily biodegradable.