1H-Imidazole, hydrobromide (1:1)

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

2004-12-13 to 2005-01-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across from imidazole hydrobromide to imidazole hydroiodide is justified since both substances only differ in the respective counterion iodide or bromide. Both anions iodide and bromide are quite similar concerning toxicological behaviour and thus do not influence the toxicological results received.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(1992)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(1992)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

, signed March 2003

Test material

Test material information

Constituent 1

Reference substance name:

1H-Imidazole hydroiodide

Cas Number:

68007-08-9

Molecular formula:

C3H4N2*HI

IUPAC Name:

1H-Imidazole hydroiodide

Test material form:

solid

Details on test material:

- Name of test material (as cited in study report): Imidazolhydroiodid
- Solubility in water: > 500 g/L
- pH in aqueous solution: 3.5 - 4.5 at concentrations of 50 g/L

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

- Method of cultivation: aerobic
- Source of inoculum/activated sludge: wastewater treatment plant, ARA Ergolz II, Füllinsdorf, Switzerland
- Preparation of inoculum for exposure: The wet sludge was suspended in test water to obtain a concentration of 4 g dry material/L. The final concentration of 30 mg dry material/L was reached by further dilution.
- Pretreatment: The sludge was washed twice with tap water by centrifugation. An aliquot of the final sludge suspension was weighed and the ratio of wet to dry weight was calculated after drying.
- Concentration of sludge: 4 g dry material/L with a final test concentration of 30 mg dry material/L

Duration of test (contact time):

21 d

Initial test substance concentration

Initial conc.:

170 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral nutrienr solution according to OECD 301
- Test temperature: 22 - 23 °C
- pH: at test start: 7.4; at test end: for test item : 7.3 - 7.4; for procedure control: 7.5; for inoculum control: 7.3; for abiotic control: 7.3; for toxicity control: 6.9
- pH adjusted: if necessary, adjusted with sodium hydroxide to pH 7.4
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2000-mL Erlenmeyer flasks
- Number of culture flasks/concentration: 2 bottles for test item, procedure control and inoculum blank each; 1 bottle for abiotic and toxicity control each
- Method used to create aerobic conditions: sludge was areated at room temperature until use.
- Measuring equipment: TOC Analyser equipped with an autosampler (Shimadzu TOC-5000A)

SAMPLING
- Sampling frequency: Samples were taken on Day 0, 3, 7, 10, 14, and 21.
- Sampling method: One sample of about 10 mL. Prior to sampling, if necessary water evaporation losses were compensated by addition of purified water. Samples were filtered (0.45 µm filter) and the first 3-4 mL were discarded.
- Sample storage before analysis: No, analysed on the day of sampling.


CONTROL AND BLANK SYSTEM
- Inoculum blank: Inoculum in medium
- Abiotic sterile control: 170 mg/L test item + 10 mg/L mercury dichloride
- Toxicity control: 170 mg/L test item + 50 mg/L reference item (sodium benzoate) + inoculum
- Other: Procedure control: 50 mg/L reference item + inoculum

STATISTICAL METHODS: Calculations performed acc. to OECD 301 A

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Test performance:

No unusual observations.

% Degradation

% Degradation 1

Parameter:

% degradation (DOC removal)

Value:

97

Sampling time:

14 d

% Degradation 2

Parameter:

% degradation (DOC removal)

Value:

90

Sampling time:

21 d

Details on results:

In the flasks containing test item and inoculum, the concentration of DOC decreased from initially 30.9 mg/L to 1.1 - 3.1 mg/L after 14 days and after 21 days, respectively.
In the abiotic control no significant elimination of DOC occured.
In the procedure control, the reference item (sodium benzoate) was completely biodegraded within three days.
In the toxicity control, the biodegradation amounted to 97% within 14 days. No inhibition of activated sludge was observed.

BOD5 / COD results

Results with reference substance:

In the procedure control, the reference item (sodium benzoate) was completely biodegraded within three days.

Any other information on results incl. tables

Percentage biodegradation corrected for the inoculum controls (except for the abiotic control)

Time (d)	Percentage biodegradation
	Test item			Procedure control			Abiotic control	Toxicity control
	Flask No.			Flask No.			Flask No.
	9	10	mean	3	4	mean	11	12
0	0	0	0	0	0	0	0	0
3	6	4	100	103	101	101	3	54
7	7	50	101	100	101	101	-4	98
10	95	97	99	100	99	99	-2	98
14	97	97	101	102	101	101	-2	97
21	88	92	99	101	100	100	-3	93

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

In a ready biodegradability DOC die-away test according to OECD 301A (1992) and EU method C.4-A (1992), the mean biodegradation of Imidazolhydroiodid was measured to be 90-97 % between Days 10 and 21 days of exposure. In the toxicity control, the test item was found to be non inhibiting to activated sludge with a decrease of 97 % of initial DOC within 14 days.
Therefore, the test substance is considered to be readily biodegradable by fullfilling the pass level of >70% removal of DOC and not inhibitoring to microorganisms by fullfilling the pass level of > 35 % degradation in the toxicity test.