Benzonitrile, 4-[(1,6-dihydro-4-hydroxy-6-oxo-2-pyrimidinyl)amino]-

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:

2015-06-09 to 2015-07-09

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

Qualifier:

according to guideline

Guideline:

ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 10634 "Water Quality - Guidance for the preparation and treatment of poorly water-soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium"

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: municipal sewage treatment plant receiving predominantly domestic sewage, 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands.
- Preparation of inoculum for exposure: sludge was kept under continuous aeration until further treatment. Before use, the sludge was allowed to settle (75 minutes) and the supernatant liquid was used as inoculum.
- Concentration of sludge: The concentration of suspended solids was determined to be 4.6 g/L in the concentrated sludge.

Duration of test (contact time):

28 d

Initial conc.:

20.8 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: test water prepared according to test guidelines, analytical grade salts dissolved in tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon. The test item directly weighed into the test flasks, Milli-RO water added, vigorous mixing (vortex). The test solutions were continuously stirred during the test and the test medium was daily swirked around.
- Additional substrate: no
- Test temperature: 22-24°C
- pH: 7.5-7.9, measured prior to testing in each test flask before addition of inoculum, and again in each test flask at the end of the incubation period
- pH adjusted: no
- Aeration of dilution water: The test solutions were continuously stirred during the test.
- Continuous darkness: yes

TEST SYSTEM
- Test flasks: 2 L glass brown coloured bottles
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: A mixture of oxygen (~20%) and nitrogen (~80%) was passed through a bottle, containing 0,5 - 1 L 0,0125 M Ba(OH)2 solution to trap CO2. The synthetic air was sparged through the scrubbing solutions at a rate of ~1-2 bubbles per second ( ~30-100 mL/min).
- Details of trap for CO2 and volatile organics if used: 3 CO2-absorbers (bottles filled with 100 mL 0,0125 M Ba(OH)2) were connected in series to the exit air line of each bottle. The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining ba(OH)2 with 0,05 M standardized HCl.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, two replicates with only inoculum
- Toxicity control: yes, one replicate with test item, reference substance, and inoculum
- Procedure control: yes, 1 replicate with reference item and inoculum

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 6

Sampling time:

28 d

Details on results:

No significant biodegradation of the test item occurred within 28 days of incubation (5% and 7%, based on ThCO2 ). The toxicity controls indicated that the test item did not have an inhibitory effect on the microbial activity.

Results with reference substance:

The positive control item was biodegraded by at least 60% (73%) within 14 days, confirming suitability of the activated sludge.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

A 28-d ready biodegradability test (OECD 301B, modified sturm test) using unadapted activated sludge from a predominantly domestic waste water treatment plant indicated that T002326 was not readily biodegradable under the conditions of the test (initial concentration 20.8 mg/L). The results of the test can be considered reliable without restriction.

Description of key information

One study (Soeter, 2015) is included in this dossier and regarded as a key study (Klimisch score of 1).  The biodegradability of T002326 was determined according to the OECD Guideline 301B and EU Method C.4-D. Under the conditions of the test, T002326 was determined to be not biodegradable within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

One study was available, measuring the ready biodegradability of T002326 over 28 dayswas determined in a carbon dioxide (CO2) evolution test (modified Sturm test) (Soeter, 2015).The test item was tested in duplicate at 20.8 mg/L, corresponding to 12 mg TOC/L.The inoculum was activated sludge. T002326 was found to be not biodegradable under the test conditions within the 28-d exposure period.