N,N''-(methylenedi-4,1-phenylene)bis[N'-octylurea]

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:

3 July- 1 August, 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes

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): water treatment plant of Evreux, France, containing effluent from a predominantly domestic origin, sampling date: 26 June 2003..
- Preparation of inoculum for exposure: air was bubbled through the inoculum until use.
- Pretreatment: the inoculum was prepared by initially decanting and sieving sewage sludge. The sludge was then centrifuged for 5 minutes, the supernatant was rejected and the pellet was redispersed in the mineral medium. In order to wash out the dissolved organic carbon (DOC) and to lower the carbon organic content, the inoculum was preconditioned for 6 days before use. Air was bubbled through the inoculum during this preconditioning period.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

other: TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: OECD 301 mineral medium
- Test temperature: 20-24 ºC
- pH: start of teh test: 7.6, end of the test: 7.9-8.28
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: 12 mg/L (dw)
- Continuous darkness: yes (dark glass bottles fitted with dark glass stoppers and aeration tubes to reduce the quantity of light reaching the test suspensions)

TEST SYSTEM
- Culturing apparatus: 3 liters test vessels, with magnetic stirrers for agitation
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: air was bubbled through each parallel at the rate of 30 - 100 mL/min during the test.

SAMPLING
- Sampling frequency: days 1, 4, 6, 8, 12, 14, 18, 22, 25 and 29
- Sampling method: For each measurement, the first wash bottle nearest to the test flask was disconnected and titrated with 0.05 M HCI, using phenolphthalein as an indicator. The remaining CO2 absorber bottles were connected to the test flasks so that the second wash bottle replaced the first one and an extra bottle containing fresh barium hydroxide solution was added to the far end of the series.
For calculation purpose, it was assumed that the volume necessary to titrate untitrated wash bottle would be the same as the volume needed to titrate 100 mL of the Ba(OH)2 stock solution. Each time CO2 was analyzed, 100 mL of the barium hydroxide stock solution (used to fill the wash bottles) was titrated with the HCl solution in order to determine the maximum amount of acid required to titrate the wash bottles.
On the 28th day, 1 mL of concentrated hydrochloric acid was added to each test flask to stop the biodegradation and test flasks were aerated overnight to drive off the remaining carbon dioxide. A final CO2 analysis of all wash bottles was made on the 29th day, this final analysis being representative of biodegradation of the 28th day.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

21

Sampling time:

28 d

Details on results:

Points of degradation plot (test substance):
1 % degradation after 1 d
1 % degradation after 4 d
2 % degradation after 6 d
4 % degradation after 8 d
6 % degradation after 12 d
9 % degradation after 14 d
13 % degradation after 18 d
14 % degradation after 22 d
17 % degradation after 25 d
21 % degradation after 28 d

Results with reference substance:

Points of degradation plot (reference substance):
7 % degradation after 1 d
32 % degradation after 4 d
49 % degradation after 6 d
60 % degradation after 8 d
60 % degradation after 12 d
64 % degradation after 14 d
70 % degradation after 18 d
70 % degradation after 22 d
71 % degradation after 25 d
72 % degradation after 28 d

All validity criteria were met:

-the biodegradation values of the test item replicates deviated by less than 20% at the end of the test,

-the biodegradation in the reference test was 64% after 14 days thus it was at least 60% within this period,

-the blank value (average of the two controls) was =< 70 mg of CO2/L at the end of the test (33.1 mg/L).

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test substance was tested for biodegradation according to OECD 301B and GLP principles. The biodegradation of the test substance reached 18% at the end of the 10-day window and 21% at the end of the test (28 days). Therefore, the test substance is not readily biodegradable in the 28-day modified Sturm test. No toxicity control was included.

Description of key information

Under the conditions of the modified Sturm test (OECD 301B), the substance was determined to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

The substance was tested for its ready biodegradation according to OECD 301B and GLP principles. A concentration of 10 mg/L was tested and all validity criteria were met. No toxicity control was included. The biodegradation of the substance reached 21% at the end of the test (28 days). Therefore, the substance is not readily biodegradable in the 28-day modified Sturm test.