bis(2,2,6,6-tetramethyl-1-(phenylthio)piperidin-4-yl)carbonate

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:

2019-06-20 - 2019-10-09

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: MEP, P.R. China, the Guideline for the Testing of Chemicals, Degradation and Accumulation (the Second Edition), No. 301F “Manometric Respirometry Test”. (2013.9)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

anaerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Remarks:

from sewage treatment plant, predominantly domestic

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage treatment plant
A fresh sample of activated sludge was collected from the aeration tank of Shenyang North Sewage Treatment Plant 2 days before the test exposure was started. It is a well functioning treatment plant receiving predominantly domestic sewage.
- Storage conditions: The suspended sludge was kept aerobic at 21.9 ~ 23.3 °C until used for the test
- Preparation of inoculum for exposure: On the day of the test beginning, 5 replicates of 10 mL sludge were weighed and dried at 105 °C for 1 hour and 50 minutes and reweighed. The measured concentration was 3854 mg/L as SS. From this result, the added amount of wet sludge was calculated.
- Pretreatment: yes, coarse particles were removed by filtration through a fine sieve and the sample was settled. After the supernatant was discarded, the sludge was washed twice with mineral medium and the concentrated sludge was suspended in mineral medium. 4 replicates of 10 mL suspended sludge was weighed and dried at 105 °C for 1 hours and 33 minutes and reweighed to calculate initial sludge concentration. The measured concentration of suspended sludge was 3.82 g/L as suspended solids (SS).
- Concentration of sludge: not greater than 30 mg/L (as suspended solids (SS))

Duration of test (contact time):

28 d

Initial conc.:

22.14 mg/L

Based on:

test mat.

Initial conc.:

53.35 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
(A) Dissolve 4.2517 g potassium dihydrogen orthophosphate (KH2PO4), 10.8758 g dipotassium hydrogen orthophosphate (K2HPO4), 16.7002 g disodium hydrogen orthophosphate dihydrate (Na2HPO4·2H2O), and 0.2505 g ammonium chloride (NH4Cl) in distilled water and make up to 500 mL. The pH of the solution was 7.59.
(B) Dissolve 3.6419 g calcium chloride dihydrate, CaCl2·2H2O in distilled water and make up to 100 mL.
(C) Dissolve 2.2507 g magnesium sulfate heptahydrate (MgSO4·7H2O) in distilled water and make up to 100 mL.
(D) Dissolve 0.0252 g iron (III) chloride hexahydrate (FeCl3·6H2O) in distilled water and make up to 100 mL.
There were no precipitates formed in above stock solutions, and the solutions were used for preparation of mineral medium.
- Test temperature: 22°C ± 1°C (actual temperature range 21.1 ~ 22.7 °C)
- pH: 7.52 and 7.54
- Continuous darkness: no, diffused light.

TEST SYSTEM
- Preparation of Inoculated Mineral Medium
About 800 mL mineral medium were added to 1 L flask, followed by the addition of 7.78 mL of the prepared activated sludge and the mixture was made up to volume to give a suspended solid concentration of 30 mg/L. The 1 L inoculated mineral medium was brought into each test vessel except abiotic sterile control test vessel.
- Test Item Test Vessels
The method of test item addition was as follows: 0.02207 g and 0.02220 g of test item was weighed and added directly to test vessel to give a final concentration of test item of 22.14 mg/L (average, 2 replicates), equivalent to 53.35 mg/L ThODNH3 in the test suspension. Test item test vessels were prepared in duplicate as test suspension (identified as TS-1and TS-2).
- Measuring of Oxygen Uptake: Respirometer system, Oxygen uptake values in all test flasks were recorded at 24 hour interval for the 28 day period by the automated respirometer

CONTROL AND BLANK SYSTEM
- Reference Item Test Vessel
A weighed quantity (0.03086 g) of reference item was added directly into test vessel. The concentration of the reference item was 30.86 mg/L sodium benzoate (equivalent to 51.54 mg/L as ThOD). Reference item test vessel was prepared in one replicate (procedure control identified as PC).
- Inoculum Blank Controls Test Vessels
Test vessels containing only 1 L inoculated mineral medium were prepared in duplicate and serve as inoculum controls identified as IC-1 and IC-2.
- Toxicity Control Test Vessel
Toxicity control test vessel contained both test item and reference item. Both, a weighed quantity (0.02209 g) of test item and a weighed quantity (0.03175 g) of reference item were added into test vessel. The concentration of test item was 22.09 mg/L (equivalent to 53.24 mg/L as ThODNH3) and the concentration of reference substance was 31.75 mg/L (equivalent to 53.02 mg/L as ThOD). The concentration expressed as total ThOD (based on ThODNH3) was 106.26 mg/L. One replicate (toxicity control identified as TC) sufficed.
- Abiotic Sterile Control Test Vessel
Abiotic sterile control test vessel contained both test item and sterilising agent. Both, 0.02226 g of test item and 0.03029 g of 3,5-dichlorophenol (3,5-DCP, a toxic substance) as a sterilising agent, were weighed and added directly into test vessel. 1 L mineral medium was brought into the test vessel. The concentration of test item was 22.26 mg/L, equivalent to 53.65 mg/L ThODNH3. The concentration of 3,5-dichlorophenol in final volume was 30.29 mg/L. No inocula were added to test flask which served as an abiotic sterile control identified as ASC. One replicate sufficed.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

NA

Parameter:

% degradation (O2 consumption)

Value:

0.4

Sampling time:

28 d

Details on results:

The biodegradation of test item after 28 days averaged 0.4% (2 replicates). The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within the 28-day period.
In the Toxicity Control (TC) test mixture, 47.3% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test.
In the Abiotic Sterile Control (ASC) test vessel, 10.4% degradation occurred after 28 days.

Results with reference substance:

The biodegradation of the reference substance (Sodium benzoate) attained 63.5% after Day 3, 97.8% after Day 14 and 103.7% after Day 28.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Based on the results, the percentage biodegradation within 28 days did not exceed the pass level of 60% ThOD. The test item did not meet the criteria for “ready biodegradability” under the described test conditions.

Executive summary:

The ready biodegradability test of the test item was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28-day test period according to OECD 301F and under GLP conditions.

The test item was added directly to test vessels at a level of 22.14 mg/L (equivalent to 53.35 mg/L as Theoretical Oxygen Demand or “ThODNH3”) (average, 2 replicate). The test concentration of sodium benzoate, used as reference substance in the Procedure Control, was 30.86 mg/L (equivalent to 51.54 mg/L as ThOD). In the Toxicity Control (TC) containing both test item and reference substance, the test item was added to the test vessel at a level of 22.09 mg/L(equivalent to 53.24 mg/L as ThODNH3) and the reference substance was added at a level of 31.75 mg/L of sodium benzoate (equivalent to 53.02 mg/L as ThOD). The concentration expressed as total ThOD was 106.26 mg/L. In the Abiotic Sterile Control (ASC), test vessel without inocula addition and containing sterilising agent, the test item was added to the test vessel at a level of 22.26 mg/L (equivalent to 53.65 mg/L as ThODNH3).

The biodegradation of test item after 28 days averaged 0.4% (2 replicates). The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within the 28-day period.

The biodegradation of the reference substance (Sodium benzoate) attained 63.5% after Day 3, 97.8% after Day 14 and 103.7% after Day 28.

In the Toxicity Control (TC) test mixture, 47.3% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. 

In the Abiotic Sterile Control (ASC) test vessel, 10.4% degradation occurred after 28 days.

Based on the results, the percentage biodegradation of the test item within 28 days did not exceed the pass level of 60% ThOD. The test item did not meet the criteria for “ready biodegradability” under the described test conditions.

Description of key information

Ready biodegradability

Key, OECD 301 F, GLP, 0.4 % in 28 days: not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Ready biodegradability

The ready biodegradability test of the test item was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28-day test period according to OECD 301F and under GLP conditions.

The test item was added directly to test vessels at a level of 22.14 mg/L (equivalent to 53.35 mg/L as Theoretical Oxygen Demand or “ThODNH3”) (average, 2 replicate). The test concentration of sodium benzoate, used as reference substance in the Procedure Control, was 30.86 mg/L (equivalent to 51.54 mg/L as ThOD). In the Toxicity Control (TC) containing both test item and reference substance, the test item was added to the test vessel at a level of 22.09 mg/L(equivalent to 53.24 mg/L as ThODNH3) and the reference substance was added at a level of 31.75 mg/L of sodium benzoate (equivalent to 53.02 mg/L as ThOD). The concentration expressed as total ThOD was 106.26 mg/L. In the Abiotic Sterile Control (ASC), test vessel without inocula addition and containing sterilising agent, the test item was added to the test vessel at a level of 22.26 mg/L (equivalent to 53.65 mg/L as ThODNH3).

The biodegradation of test item after 28 days averaged 0.4% (2 replicates). The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within the 28-day period.

The biodegradation of the reference substance (Sodium benzoate) attained 63.5% after Day 3, 97.8% after Day 14 and 103.7% after Day 28.

In the Toxicity Control (TC) test mixture, 47.3% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. 

In the Abiotic Sterile Control (ASC) test vessel, 10.4% degradation occurred after 28 days.

Based on the results, the percentage biodegradation of the test item within 28 days did not exceed the pass level of 60% ThOD. The test item did not meet the criteria for “ready biodegradability” under the described test conditions.