2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol

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:

2016-10-20 till 2017-08-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EC) No 440/2008, Annex Part C, C.4., Part IV: “CO2 Evolution Test (Method C.4-C)”

Version / remarks:

May 30, 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Jusly 17, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Version / remarks:

January 1998

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge from a domestic waste water treatment plant
- Origin: sewage plant Balonfüred, Hungary
- Preparation of inoculum for exposure: The sludge was washed by centrifugation. The solid material was re-suspened in isotonic saline solution by shaking and centrifuging. This procedure was repeated twice. An aliquot of the final sludge suspension was weighted, dried and the ratio of wet sludge to dry weight determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 5 g dry material/L was mixed with mineral medium and then aerated under test conditions (for 6 days) until use. A pH adjustment of activated sludge inoculum was not performed.
- Pretreatment: Pre-conditioning consisted of aerating (2 L/min) activated sludge (in mineral medium) for 6 days at the test temperature (20.1 - 21.9 °C).
- Concentration of sludge: 5 g/L
- Initial cell/biomass concentration: call count of approx. 1E7 - 1E8/L
- Water filtered: yes
- Type and size of filter used, if any: cotton and coarse filter paper

Duration of test (contact time):

28 d

Initial conc.:

33 mg/L

Based on:

test mat.

Remarks:

corresponds to 15 mg organic DOC/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: According to the OECD TG 301B (In solution b) CaCl2*2H2O was used and d) was immediately prepared before use without any additive).
- Test temperature: 20.1 - 21.1 °C
- pH: approx. 7.58 (on day 28)
- pH adjusted: at study start to 7.38 (with 1N HCl)
- Aeration of dilution water: no
- Suspended solids concentration: approx. 25 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: glass flasks (5000 mL)
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration with CO2-free air at a rate of about 60 mL/min.
- Measuring equipment: The total carbon, inorganic carbon and dissolved organic carbon of the centrifuged samples were measured with Shimadzu Total Organic Carbon Analyzer (TOC-L CSH type).

SAMPLING
- Sampling frequency: on days 0, 2, 4, 6, 8, 11, 15, 20, 25, 28 and 29

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Toxicity control: Yes

STATISTICAL METHODS: according to OECD TG 301B

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

11.89

Sampling time:

28 d

Details on results:

Under the test conditions, the percentage degradation of the test item reached a mean on 11.89 % after 28 days of incubation.
In the toxicity control containing both, the test item and the reference item, a mean of 27.25 % biodegradation was noted within 8 days and 35.52 % biodegradation after 28 days of incubation.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded 61.74 % after 6 days, and to 76.22 % after 28 days of incubation, thus confirming the suitability of the used activated sludge inoculum.
In the toxicity control containing both, the test item and the reference item, a mean of 27.25 % biodegradation was noted within 8 days and 35.52 % biodegradation after 28 days of incubation.

Table 1: Percentage Biodegradation at Different Time Intervals during the Exposure Period of 28 Days Calculated Based on ThCO₂

Test group	Flask number	Percentage Biodegradation after n days of exposure (%)
		2	4	6	8	11	15	20	25	28
Test item group	1	1.54	2.43	4.48	5.58	7.70	10.33	10.17	11.18	11.73
	2	0.77	2.08	3.88	6.27	7.49	8.88	12.30	11.57	12.05
Mean		1.16	2.25	4.18	5.92	7.59	9.61	11.23	11.38	11.89
Procedure control	5	7.85	38.17	61.74	67.42	72.83	72.46	74.93	75.78	76.22
Toxicity control	6	2.61	13.78	22.21	27.25	31.80	31.12	34.69	34.63	35.52

 

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, not fulfilling specific criteria

Conclusions:

The test item was considered to be not readily biodegradable. According to the test guidelines the pass level for ready biodegradability is 60 % of ThCO2. The above result was confirmed by a TC, IC and DOC analysis of test item containing samples taken at the start and end of the test. According to the test guidelines followed, the test item can be assumed to not inhibit the activated sludge microorganisms, because the degradation in the toxicity control group was higher than 25 % within 14 days.

Executive summary:

The test item was investigated for its ready biodegradability in a study according to OECD TG 301B under GLP at the concentration of 33 mg/L. The test was performed over a period of 28 days with biodegradation that was followed by CO2-evolution. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The percentage biodegradation of the test item reached a mean of 11.98 % after 28 days. The reference item Sodium benzoate was sufficiently degraded to 61.74% already after 8 days, and to 76.22 % after 28 days of incubation, based on its ThCO2, thus confirming the suitability of the used activated sludge inoculum. In the toxicity control containing both the test item and the reference item, a mean of 27.25 % biodegradation was noted within 8 days and 35.52 % biodegradation after 28 days of incubation. Since all acceptability criteria prescribed by the protocol were met, this study was considered valid. In conclusion, the test item was considered to be inherently, primarily biodegradable, as a 10-d-window could not be determined during the 28-day test.

Description of key information

In a study according to OECD TG 301B under GLP, the substance is found to be inherently, primarily biodegradable (reference 5.2.1-1).

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Type of water:

freshwater

Additional information

The test item was investigated for its ready biodegradability in a study according to OECD TG 301B under GLP at the concentration of 33 mg/L. The test was performed over a period of 28 days with biodegradation that was followed by CO2-evolution. As a reference item, sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The percentage biodegradation of the test item reached a mean of 11.98 % after 28 days. The reference item Sodium benzoate was sufficiently degraded to 61.74% already after 8 days, and to 76.22 % after 28 days of incubation, based on its ThCO2, thus confirming the suitability of the used activated sludge inoculum. In the toxicity control containing both the test item and the reference item, a mean of 27.25 % biodegradation was noted within 8 days and 35.52 % biodegradation after 28 days of incubation. Since all acceptability criteria prescribed by the protocol were met, this study was considered valid. In conclusion, the test item was considered to be inherently, primarily biodegradable, as a 10-d-window could not be determined during the 28-day test.