N,N-bis(2-hydroxypropyl)benzamide

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:

From May 14th to June 29th, 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

The study was performed with aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Fullinsdorf, Switzerland) treating predominantly domestic wastewater.
The sludge was washed once with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed. thereafter dried and the ratio of wet to dry weight was calculated.
Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4g dry material per liter. During holding, the sludge was aerated at room temperature until use.
Test water was inoculated with defined volumes of this diluted activeted sludge to gove a final concentration of 30 mg dry material per liter.

Duration of test (contact time):

45 d

Initial conc.:

44 mg/L

Based on:

test mat.

Initial conc.:

28.8 mg/L

Based on:

DOC

Remarks:

Flask 1

Initial conc.:

28.3 mg/L

Based on:

DOC

Remarks:

Flask 2

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Test water was prepared according to testing guideline. Analytical grade salts were dissolved in purified water to obtain the following stock solutions:
a) KH2PO4 8.5 g/L
K2HPO4 21.75 g/L
Na2HPO4 * 2H2O 33.4 g/L
NH4Cl 0.5 g/L
The pH of this solution was 7.4

b) MgSO4 * 7H2O 22.5 g/L
c) CaCl2 * 2H2O 36.4 g/L
d) FeCl * 6H2O 0.25 g/L

In order to avoid having to prepare solution d) immediately before use, one drop of concentrated HCl per liter was added.
To obtain the final test water, 10 mL of stock solution a) and 1 mL each of stock solutions b) and d) were combined and made up to 1000 mL with purified water. The pH was adjusted to 7.4 with a diluted hydrochloric acid solution.

- Test temperature: 23-24 °C
- pH: 7.3 - 7.4 prior to the test, 7.1-7.4 at the end of incubation.
- Test duration: 45 days. In accordance with the testing guideline the test was prolonged beyond 28 days since the biodegradation curve of test item showed that biodegradation had started but the plateau has not been reached.
- Continuous darkness: yes

SAMPLING
Samples were taken on Day 0 (treatment day), 3, 7, 10, 14, 21, 27, 28, 35, 42 and 45 of the incubation period for DOC analysis. One sample of about 10 mL was taken from each test flask per sampling date. Prior to sampling, water evaporation losses were determined by weighing the flasks and were compensated by adding purified water. Deposits on the test vessels were scraped off and resuspended in the test vassel.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

< 10

Sampling time:

21 d

Key result

Parameter:

% degradation (DOC removal)

Value:

21

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

74

Sampling time:

45 d

Details on results:

Concentration of DOC decreased only slightly after 28 days, while biodegradation happened in the period from 28th to 45th day of experiment.
In the abiotic control, no degradation occured under test conditions.
In the toxicity control, containing test item (48.8% of the total DOC), the reference substance (51.2% of the total DOC) and activeted sludge, the degradation was 56% after 14 days, therefore test item is not inhibiting the activeted sludge.

Results with reference substance:

In the procedure controls containing reference item sodium benzoate and activated sludge, biodegradation was complete within 7 days of exposure, confirming suitability of the activated sludge used

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The substance was found to be biodegradable under test conditions over a 45-day exposure to activated sludge (74% of DOC removal). However, the pass level for ready biodegradability (70% DOC removal within a 10-day window) was not reached during a 28-day test period.

Executive summary:

Ready biodegradability of the substance was investigated in a study according to OECD TG 301 A. In accordance with the guideline the test was prolonged to 45 days since the biodegradation curve of the test item showed that biodegradation had started after 21 days but the plateau had not been reached after the regular test period of 28 days.

In the test flasks containing test item and activated sludge the mean concentration of DOC decreased only slightly after 28 days (21% of degradation), while biodegradation happened in the period from 28th to 45th day of experiment (74% of degradation at day 45).

The reference item sodium benzoate was completely biodegraded within 7 days of exposure, confirming suitability of the activated sludge used. In the abiotic control, no degradation occured under test conditions. In the toxicity control, containing test item (48.8% of the total DOC), the reference substance (51.2% of the total DOC) and activeted sludge, the degradation was 56% after 14 days, therefore test item is not inhibiting the activeted sludge.

Results from the controls confirmed the validity of the study, which showed biodegradation of test substance after 45 days. However, the pass level for ready biodegradability (70% DOC removal within a 10-day window) was not reached during a 28-day test period.

Therefore, the substance has to be considered not readily biodegradable.

Description of key information

In a study according to OECD TG 301 A, the substance showed a degradation of 21% by activated sludge after 28 days of treatment. Therefore, it was considered to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed