2-phenylimidazole

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1st test: 14 Sep - 26 Sep 2017; 2nd test: 19 Oct - 17 Nov 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

July 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Karlsruhe, Germany

Test material

Test material information

Constituent 1

Reference substance name:

2-phenylimidazole

EC Number:

211-581-7

EC Name:

2-phenylimidazole

Cas Number:

670-96-2

Molecular formula:

C9H8N2

IUPAC Name:

2-phenyl-1H-imidazole

Test material form:

solid: flakes

Study design

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): AZV Staufener Bucht, sampled on 23 Oct 2017
- Storage length: 1 day between sampling and start of incubation of the test item
- Preparation of inoculum for exposure: drying at 105 °C for 5 hours, washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge
- Concentration of sludge: 30 mg dry solids/L

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 20.6 - 24.0 °C.
- Aeration of dilution water: tolerated range of 1.6 – 5.5 bubbles/second (counted bubbles: 2.4 – 5.1 bubbles/second)
- Suspended solids concentration: 30 mg dry solids/L

TEST SYSTEM
- Culturing apparatus: Gas wash bottles (2000 mL volume)
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: The CO2-free air production system consists of an air compressor, three 1000 mL gas wash bottles filled with dry soda lime in series followed by one bottle filled with 0.1 M NaOH (sodium hydroxide). At the end of the system is one gas wash bottle filled with demineralised water, followed by an empty one to catch any drops of condensation water. A color change of the soda lime from white to blue indicates that the CO2 absorption capacity is depleted. The CO2-free air is passed on to an air distributor with two input and 22 output channels and through PE-tubes.
- Measuring equipment: Degradation is followed by determining the carbon dioxide produced and absorbed to sodium hydroxide via IC-measurement (IC=inorganic carbon).

SAMPLING
- Sampling frequency: Sampling for IC measurement took place on days days 0, 4, 7, 11, 14, 21, 28 and 29.
- Sampling method: Sampling was performed through the lateral connecting pieces through the butyl rubber septum using 5 mL PE syringes.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, three bottles
- Toxicity control: yes, one bottle
- Reference substance: yes, three bottles

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Remarks:

based on ThCO2

Value:

0

Sampling time:

28 d

Details on results:

The degradation extent in the toxicity control was 44.7% within 14 days. The test material is there considered to have no inhibitory effect on the inoculum.
For details on biodegradation rates, please refer to Table 1 in section "Any other information on results incl. tables".

BOD5 / COD results

Results with reference substance:

The reference substance reached the pass level for ready biodegradability within 4 days. The degradation after 28 days was 89.5 - 97.8%.

Any other information on results incl. tables

Table 1: Ultimate biodegradation after x days [% of ThCO2]

Reactor		Days
		0	4	7	11	14	21	28	29
15	Test flasks	0	2.2	2.2	3.3	4.2	3.3	2.7	4.3
16		0	-0.5	-2.1	-3.0	-3.4	-6.4	-7-0	-5.9
17		0	-1.6	-2.1	-3.6	-3.5	-8.7	-9.4	-9.2
4	Reference flasks	0	68.7	84.1	86.3	87.3	101.4	89.5	89.9
5		0	80.9	89.9	92.2	92.2	106.6	97.8	99.3
6		0	73.9	86.4	86.3	88.9	107.2	96.3	98.3
18	Toxicity control (Test item and reference item)	0	35.1	42.4	43.7	44.7	48.7	44.6	45.3

Table 2: Validity criteria of the 2nd main test

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	< 20%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	87.3 -92.2%	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	44.7%	yes

The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	< 5%	yes
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	29.9 mg/L	yes

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The 1st test was terminated since the validity criterion "difference of replicate values < 20%" was not fulfilled. The 2nd main test fulfilled the validity criteria. For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

under test conditions no biodegradation observed