3-pyridylmethanol

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 2017-06-12 to 2017-08-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

TOXI-COOP ZRT., 8230 Balatonfüred, Arácsi út 97., Hungary

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: sewage plant for domestic sewage in Balatonfüred, Hungary
- Storage length: 6 days before the main test
- Preparation of inoculum for exposure: The inoculum was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in isotonic saline solution and again centrifuged. This procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 5 g dry material per litre was mixed with test water (mineral medium, see above) and then aerated under test conditions (for 6 days) until use. The pH of the activated sludge inoculum after preparation was 7.13, just before use: 7.18.
- Pretreatment: Pre-conditioning consisted of aerating (2 L/minute) activated sludge (in mineral medium) for 6 days at the test temperature (the actual temperature: 20.0 – 21.6 °C). During the pre-conditioning the approximately cell count of aerated inoculum was in the range of ~10^8/L; therefore, before the test the inoculum was further diluted 20 000x with mineral medium to reach the necessary ~10^4 - 10^5 cells/L cell concentration.
- Concentration of sludge: 5 g dry material/L
- Initial cell/biomass concentration: ~10^4 - 10^5 cells/L
- Water filtered: no
- Type and size of filter used, if any: After preparation the sludge was filtered through cotton wool.

Duration of test (contact time):

28 d

Initial conc.:

5.73 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium used. Prepared according to OECD 301.
- Test temperature: 20.1 - 21.4 °C
- pH: 7.22
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: 5 g dry material/L
- Continuous darkness: yes
- Oxygen concentration of the test water: About 8 - 9 mg/L (was measured at the start of the test and found to be 8.48 mg/L).

TEST SYSTEM
- Culturing apparatus: Winkler bottles (300 mL, coded) with special neck and glass stoppers.
- Number of culture flasks/concentration: 16 (+ 2 reserve) bottles containing the test item and inoculum; 16 (+ 2 reserve) bottles containing the reference item and inoculum (procedure control);
- Measuring equipment: The oxygen concentration was measured with an O2 electrode.

SAMPLING
- Sampling frequency: in all duplicate bottles in all groups on days 0, 1, 2, 5, 7, 14, 21 and 28.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 16 (+ 2 reserve) bottles containing only inoculum (inoculum control)
- Toxicity control: 16 (+ 2 reserve) bottles containing the test item, reference item and inoculum (toxicity control)

Reference substance:

benzoic acid, sodium salt

Preliminary study:

No toxic effect of the test item was found at the investigated concentration - 3.0 mg/L.

Key result

Parameter:

% degradation (O2 consumption)

Value:

81.9

Sampling time:

28 d

Details on results:

Under the test conditions the percentage biodegradation of the test item reached a mean of 81.9 % after 28 days based on its ThOD. The test item biodegradation (67.3 % on day 5) was above the pass level of 60 % of ThOD on the fifth day of the test consequently fulfilled the criterion for ready biodegradability since it surely reached the pass level of 60 % of ThOD in a 10-day window within the 28-d period of the test.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to a mean of 71.1 % after 14 days, and to a mean of 79.6% after 28 days of incubation, based on its ThOD.

Biodegradation of Toxicity Control

In the toxicity control containing both, the test item and the reference item, a mean of 62.2 % biodegradation was noted within 14 days and a mean of 62.1 % biodegradation was determined after 28 days of incubation.

Correction for oxygen uptake for interference with nitrification

Because of the N-containing test item, the oxidised nitrogen (nitrate and nitrite) concentrations were determined following each oxygen measurement with photometric method using nitrite and nitrate cell tests. The LOQ (Limit Of Quantification) of the measurements was 0.03 mg NO2/L and 0.4 mg NO3/L, respectively.

The measured quantities of nitrite in the inoculum control, test item and toxicity control samples were below the LOQ in the some of the samples. In other measurements they were as high as 1.2 mg/L. The oxygen uptake resulting from a possible ammonium oxidation did not influence the amount of oxygen taken up by microbial population. Therefore, any correction of the measured dissolved oxygen concentrations was considered as not necessary or not possible.

Results

Table 1. Percentage Biodegradation at Different Time Intervals during the Exposure Period of 28 Days

Treatment	Concentration	Flask	Percent of biodegradation after n days of exposure
	[mg/L]	No.	1	2	5	7	14	21	28
Test item		1a	-0.5	13.9	64.8	80.0	81.2	77.7	81.5
	3.0	1b	1.9	9.3	69.7	73.0	78.6	79.7	82.4
		mean	0.7	11.6	67.3	76.5	79.9	78.7	81.9
Reference item		2a	41.0	48.7	64.2	64.4	68.6	74.8	75.7
	3.0	2b	42.2	56.1	62.4	67.8	73.6	80.2	83.5
		mean	41.6	52.4	63.3	66.1	71.1	77.5	79.6
Toxicity control	Test item: 3.0 Reference item: 3.0	4a	27.6	33.0	45.4	57.2	62.1	62.8	62.3
		4b	28.3	34.7	48.7	61.7	62.3	63.0	62.0
		mean	28.0	33.8	47.0	59.4	62.2	62.9	62.1

Table 2. Nitrate concentrations

Analytical measurements of the x^thday samples	Measured nitrate concentration (mg/L) in the test bottles
	1A	1B	3A	3B	4A	4B
Day 0	---	< 0.4	---	---	---	---
7^thday	---	< 0.4	---	< 0.4	---	< 0.4
14^thday	< 0.4	< 0.4	---	---	---	---
21^stday	1.1	0.8	0.6	0.7	---	---
28^thday	1.2	1.1	0.9	0.7	---	---

Remark: 1A, 1B, 3A, 3B, 4A and 4B are the bottle numbers.

Limit of Quantification (LOQ) = 0.4 mg/L

--- : nitrate concentrations were not detectable.

Table 3. Nitrite concentrations

Analytical measurements of the x^thday samples	Measured nitrite concentration (mg/L) in the test bottles
	1A	1B	3A	3B	4A	4B
Day 0	---	---	---	---	---	---
7^thday	< 0.03	< 0.03	---	---	---	---
14^thday	0.07	< 0.03	0.03	---	---	---
21^stday	0.41	0.45	0.38	0.39	---	---
28^thday	0.67	0.70	0.81	0.76	---	---

Remark: 1A, 1B, 3A, 3B, 4A and 4B are the bottle numbers.

Limit of Quantification (LOQ) = 0.03 mg/L

--- : nitrite concentrations were not detectable.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test item is considered to be ready biodegradable. The pass level for ready biodegradability of 60 % ThOD removal in a 10-day window was fulfilled. The biodegradation percentage at the 28 day mark was 81.9 %.

Executive summary:

The ready biodegradability of the test item was determined with a non adapted activated sludge over a test period of 28 days in the Closed bottle test according to OECD 301D, Regulation (EC) No. 440/2008 Method C.4 -E and EPA OPPTS 835.3110 and under GLP. The test item was tested at a concentration of 3 mg/L in triplicates, corresponding to an oxygen content of 5.73 mg O2/L. The oxygen concentration was measured with an O2 electrode [working based on LDO (Luminescent Dissolved Oxygen) method]. The biodegradation of the reference item was not inhibited by the test item in the toxicity control. The biodegradation of the test item came to 81.9 % after 28 days. In conclusion, the test item is readily biodegradable as the pass level of 60 % degradation was reached in a 10-d-window within the 28 days period of the study.

Description of key information

The test item is considered to be ready biodegradable. The pass level for ready biodegradability of 60 % ThOD removal in a 10-day window was fulfilled. The biodegradation percentage at the 28 day mark was 81.9 %.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability of the test item was determined with a non adapted activated sludge over a test period of 28 days in the Closed bottle test according to OECD 301D, Regulation (EC) No. 440/2008 Method C.4 -E and EPA OPPTS 835.3110 and under GLP. The test item was tested at a concentration of 3 mg/L in triplicates, corresponding to a carbon content of 5.73 mg C/L. The biodegradation of the test item was followed by TOC analyses of the quantity of dissolved oxygen concentration. The biodegradation of the reference item was not inhibited by the test item in the toxicity control. The biodegradation of the test item came to 81.9 % after 28 days. In conclusion, the test item is readily biodegradable as the pass level of 60 % degradation was reached in a 10-d-window within the 28 days period of the study.