Bis(hydroxyethyl) terephthalate

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:

Experimental Starting Date 16. Aug. 2021
Experimental Completion Date 22. Sep. 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

2008

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: BHET
Batch no.: AWS0274J
Purity: ~95%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activation basin of the sewage treatment plant, In den Seewiesen, 67482 Edenkoben
- Pretreatment: The sludge was filtrated through a cloth, washed with test medium (2x) and resuspended in test medium. It was then aerated until use.
- Concentration of sludge: The dry matter was determined to contain 3.96 g of suspended solids/L

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

IC (inorganic carbon)

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Composition of medium:
- Solution a: Potassium dihydrogen phosphate, Dipotassium hydrogen phosphate, Disodiumhydrogen phosphate dihydrate, Ammonium chloride, Water
- Solution b: Calcium chloride dihydrate, Water
- Solution c: Magnesium sulphate heptahydrate, Water
- Solution d: Iron(III) chloride hexahydrate, Di-sodium-ethylene diaminetetraacetate dihydrate, Water
- Test Medium: Freshly prepared. 10 mL of solution a were mixed with 800 mL water, then 1 mL of solutions b, c and d were added and filled up to 1 L with water

- Test temperature: 19.7 – 21.9 °C without direct lighting
- Inoculum concentration: 25.0 mg/L

TEST SYSTEM
The test vessels were aerated with purified, CO₂-scrubbed, moistened air. The scrubbing of carbon dioxide was achieved by bubbling the purified air through a flask containing 1.5 M NaOH. To control the absence of CO₂, the air was then led through a flask containing a solution of Ba(OH)₂ before reaching the test vessels.
Magnetic stirrers were used to prevent deposition of inoculum.
The emitted CO₂ was trapped in 0.25 M NaOH. Two scrubbers containing 100 mL each were connected in series to the test vessels.

Apparatus blanks: 2, containing mineral medium only
Blank controls: 2, containing mineral medium and inoculum
Positive control flasks: 2, containing positive control, mineral medium and inoculum
Test flasks: 2, containing test item, mineral medium and inoculum
Abiotic control: 1, containing test item, mineral medium and HgCl₂
Toxicity control: 1, containing test item, positive control, mineral medium and inoculum

SAMPLING
From each front scrubber flask, 9 samples were taken in order to determine the emitted CO₂ (on day 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO₂.
On day 0, only one sample of 0,25 M NaOH was sampled. This measured value was used as start value for all treatments.
On day 28, 5 mL HCl₂ M was added to each test flask in order to drive off dissolved CO₂. On day 29, samples from both scrubber flasks were taken.

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Value:

87

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

82

Sampling time:

14 d

Parameter:

% degradation (CO2 evolution)

Value:

35.1

Sampling time:

4 d

Details on results:

Degradation behaviour of positive control and toxicity control was normal.
Abiotic degradation was not observed.
The test item is not toxic towards the inoculum in a concentration of 38.4 mg/L.

Validity criteria

Inorganic carbon content of test item solution in medium: < 5% of total carbon - valid (0%)

CO₂ emitted by the controls: < 70 mg/L - valid (10.9 mg/L)

Difference within replicates: <20% - valid (2.3%)

Degradation of positive control ≥ 60%: ≤ 14 days - valid (7 days)

Degradation in the toxicity flask on day 14: > 25% - non-toxic (85.5%)

Results with reference substance:

83.6% degradation of aniline within 29-days

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test item is readily biodegradable; 87% in 28-days

Executive summary:

The test item was tested using a concentration of nominally 20 mg organic carbon/L in test medium following OECD 301B and EU-Method C.4-C and according to GLP.

 

Aniline was chosen as positive control.  Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.  All validity criteria were met. Degradation of the positive control surpassed the pass level of 60 % after 7 days.

 

The following data were determined for the test item:

10-day-window: day 3 – 13

degradation at the end of 10-day-window: 80 %

degradation at the end of the test: 87 %

 

Therefore, when applying the 10-day-window, the test item is readily biodegradable following OECD 301B and EU C.4-C respectively.

Description of key information

The test item is readily biodegradable; 85% in 28-days.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater