4-Nitrophenyl 2-(methylsulphonyl)ethanoate

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 2020-12-14 to 2021-01-11

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:

17th July 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: 4425-191127
Purity: 99.8%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of activated sludge: collected from the aeration tank of Shenyang North Sewage Treatment Plant
- Preparation of inoculum for exposure:
- Pretreatment: On the day of sludge collection, 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.
- Storage: The suspended sludge was kept aerobic at 21.7 ~ 22.9 ℃ until used for the test.
- Concentration of sludge: 4.424 g/L as suspended solids (SS)
- Initial cell/biomass concentration: 30 mg/L (as suspended solids (SS))
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

79.3 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
The stock solutions were prepared as follows using analytical grade reagents, except that Na2HPO4·2H2O was HPLC grade.
(A) Potassium dihydrogen orthophosphate, KH2PO4 4.2500 g
Dipotassium hydrogen orthophosphate, K2HPO4 10.8752 g
Disodium hydrogen orthophosphate dihydrate, Na2HPO4·2H2O 16.7003 g
Ammonium chloride, NH4Cl 0.2501 g
Dissolve in distilled water and make up to 500 mL. The pH of the solution was 7.65, and adjusted to 7.48 with HCl.
(B) Calcium chloride dihydrate, CaCl2·2H2O 3.6401 g
Dissolve in distilled water and make up to 100 mL.
(C) Magnesium sulphate heptahydrate, MgSO4·7H2O 2.2502 g
Dissolve in distilled water and make up to 100 mL.
(D) Iron(III) chloride hexahydrate, FeCl3·6H2O 0.0250 g
Dissolve 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.
For 1 liter of mineral medium, 10 mL stock solution A was added to approximately 800 mL distilled water and the mixture stirred before adding, sequentially, 1 mL each of stock solutions B, C and D. After mixing, the mixture was made up to 1 liter with distilled water. 5 L mineral medium was prepared. The pH was checked to be 7.62, adjusted to be 7.55 with HCl.
- Test temperature: 22℃±1℃ (actual temperature range 21.2-22.4 ℃)
- pH: measured at the end of the incubation period (on Day 28), 7.21-7.83
- pH adjusted: no
- Aeration of dilution water: no
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Biochemical incubator
- Number of culture flasks/concentration: 2
- Measuring equipment: BOD analyzer
- BOD analyzer operation: After the test vessels were prepared, the following operation was performed as soon as possible: insert the magnetic stirring rod, place 2 pill of NaOH into the seal gasket. Then insert the gasket in the neck of the bottle. Screw the BOD measuring head to the BOD sample bottles. Place the sample bottles in the inductive stirring system. Keep the BOD system in the biochemical incubator in constant temperature (22±1℃) and start the stirring and the measurement of BOD values. The BOD values in all test vessels were recorded on an interval of 5 or 6 hours during the 28 day period by the automatic respirometer. At the end of the period of incubation, read the BOD values. Incubation temperature was measured continuously with minimum/maximum thermometer and the minimum and maximum values were recorded on every working day during the test.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Test vessels containing only 250 mL inoculated mineral medium were prepared in duplicate and served as inoculum controls.
- Reference Item control: A weighed quantity (0.01264 g) of reference item was added directly into test vessel. The concentration of the reference item was 50.6 mg/L sodium benzoate (equivalent to 84.5 mg/L as ThOD). Reference item test vessel was prepared in one replicate.
- Toxicity control: Toxicity control test vessel contained both test item and reference item. Both, a weighed quantity (0.01960 g) of test item and a weighed quantity (0.01295 g) of reference item were weighed and added into test vessel. The concentration of test item was 78.4 mg/L (equivalent to 106.6 mg/L as ThODNO3) and the concentration of reference substance was 51.8 mg/L (equivalent to 86.5 mg/L as ThOD). The concentration expressed as total ThOD (based on ThODNH3) was 193.1 mg/L. One replicate (toxicity control identified as TC) sufficed.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

87

Sampling time:

28 d

Details on results:

According to the results of nitrate and nitrite determination, complete nitrate occurred and no nitrite occurred at the end of the test. ThODNO3 was used to calculate the percentage biodegradation.
Based on the percentage biodegradation expressed as average, the percentage biodegradation of test item after 3 days averaged 21.0% (2 replicate), which was the initial time on which 10% biodegradation was exceeded, and when the 10-day window began. The percentage biodegradation were 79.8% (2 replicate) within 10-day window (after 13 days and 1 hours), and 87.0% after 28 days.
In the Toxicity Control (TC) test mixture, 84.5% 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.

Results with reference substance:

The biodegradation of the reference substance (Sodium benzoate) attained 61.9% after 2 day and 19 hours, 83.5% after Day 14 and 89.5% after Day 28.

Validity of the Test

The following validity criteria were met by this test:

1. The oxygen uptake of the inoculum blank was 13.25 mg O₂/L in 28 days, which did not exceed 60 mg O₂/L.


2. The pH values were in the range of 7.21– 7.83, which were in the range of 6-8.5.


3. The difference of extremes of replicate values of the removal of the test item at the end of the test was 2.2%, it was less than 20%, which is specified criterion in test guideline.


4. The percentage degradation of the reference item reached 69% after 2 days and 19 hours, 83.5% after Day 14 which exceeded the required pass level (the percentage degradation of reference item after day 14 ≥ 60%).


5. In Toxicity Control (TC), test mixture containing both test item and reference item, 25.9% degradation occurred within 1 day and 15 hours and 84.5% within 14 days based on total ThOD. Since these values exceeded the 25% ThOD limit for toxicity control, it was concluded that the test item is not inhibitory to sludge micro-organisms.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Based on the results, the percentage biodegradation of test item in 10-day window within 28-day period exceeded the pass level of 60% ThOD. The test item met the criteria for “ready biodegradability” under the described test conditions.

Executive summary:

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

The test item was added directly to test vessels at a level of 79.3 mg/L (equivalent to 107.8 mg/L as Theoretical Oxygen Demand or “ThODNO3”) (average, 2 replicates).

Based on the percentage biodegradation expressed as average, the percentage biodegradation of test item after 3 days averaged 21.0% (2 replicate), which was the initial time on which 10% biodegradation was exceeded, and when the 10-day window began. The percentage biodegradation were 79.8% (2 replicate) within 10-day window (after 13 days and 1 hours), and 87.0% after 28 days.

Based on the results, the percentage biodegradation of test item in 10-day window within 28-day period exceeded the pass level of 60% ThOD. The test item met the criteria for “ready biodegradability” under the described test conditions.

Description of key information

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

Based on the percentage biodegradation expressed as average, the percentage biodegradation of test item after 3 days averaged 21.0% (2 replicate), which was the initial time on which 10% biodegradation was exceeded, and when the 10-day window began. The percentage biodegradation were 79.8% (2 replicate) within 10-day window (after 13 days and 1 hours), and 87.0% after 28 days.

Based on the results, the percentage biodegradation of test item in 10-day window within 28-day period exceeded the pass level of 60% ThOD. The test item met the criteria for “ready biodegradability” under the described test conditions.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater