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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017.11.17 - 2018.01.30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Chemical name: DS-PHYTOSPHINGOSINE
Lot No.: PYFF01
Date received: 2017. 11. 10.
Amount: 75.18 g(including container)
Manufacturing date: 2017. 06. 01.
Expiration date: 2019. 05. 31.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Inoculum used in this study was collected from 11 sites in Korea including 5 rivers (Gangjeong, Mulgeum, Gwangju, Gapcheon, Paldang), 4 domestic sewage treatment plants (Dalseo, Gumi, Busan, Tancheon) and 2 industrial wastewater treatment plants (Dalseo, Yeosu). Fresh samples collected from these sites were incubated for over one month and the activated sludge greater than 107 cells/mL was used in this test.
Duration of test (contact time):
28 d
Initial conc.:
ca. 100 mg/L
Based on:
test mat.
Remarks:
(w/v)
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
by BOD meter
Parameter followed for biodegradation estimation:
test mat. analysis
Remarks:
by LC-MS/MS analysis
Details on study design:
Test Conditions
The test was performed in the incubator to maintain a constant temperature and the oxygen uptake was checked once a day during test period.

- Concentration of test substance : 99.9 ~ 100.1 mg/L(w/v)
- Concentration of inoculum : About 107 ~ 108 cells/L
- Temperature : 24.0 ~ 25.9 C
- Test period : 28 days
- Condition : Darkness and agitation

Biodegradation test by the BOD meter
Oxygen uptake was measured by the BOD meter equipped with 6 bottles. Reference compound, Sodium benzoate, was used to check the microbial activity of treated inoculums. Test substance and reference compound were treated to be about 100 mg/L (w/v) after correcting for purity. Six bottles for biodegradation test will be prepared as follows:

- Bottle 1(Abiotic control): Test substance(16.21 mg)
+ deionized water 160 mL

- Bottle 2, 3, 4(Treatments): Test substance(16.20 ~ 16.23 mg)
+ activated sludge 4.1 mL
+ basal culture medium 1.92 mL
+ deionized water 154 mL

- Bottle 5(Activity control): Sodium benzoate(16.10 mg)
+ activated sludge 4.1 mL
+ basal culture medium 1.92 mL
+ deionized water 154 mL

- Bottle 6(Inoculum blank): Activated sludge 4.1 mL
+ basal culture medium 1.92 mL
+ deionized water 154 mL

Temperature in the incubator was checked once a day during BOD measurement (28 days) using datalogger (T&D Corporation_Japan). For all test bottles, pH of the test solution was measured at the end of BOD measurement.

BOD meter: WTW, OxiTop® Control 6, Germany
Reference substance:
benzoic acid, sodium salt
Remarks:
Sodium benzoate
Key result
Parameter:
% degradation (O2 consumption)
Value:
>= 66 - <= 69.1
St. dev.:
1.44
Sampling time:
28 d
Key result
Parameter:
% degradation (test mat. analysis)
Value:
97
Sampling time:
29 d
Details on results:
The change of BOD concentrations for the test bottles was measured by BOD meter for 28 days. The difference of replicate value for the treatments(bottle 2, 3 and 4) at the end of the test was 2.1 % which was less than 20 % specified by the OECD guideline. The percentage biodegradations of test substance, Phytosphingosine, based on BOD measurement were calculated with a range of 66.0 ~ 69.1 % and the average percentage biodegradation was calculated to be 68.0 % after 28 days.

The percentage biodegradations based on the residual amount of test substance by LC-MS/MS analysis was calculated to 97.0 %.

BOD concentrations of the inoculum blank (bottle 6) for 28 days were 0 ~ 42.2 mg O2/L. These values were within the acceptable range (less than 60 mg O2/L for inoculums blank) specified by the OECD guideline.

There was no environmental condition which might have affected the reliability of the test results and the test temperature was maintained at 24.0 ~ 25.9 (25.1 ± 0.2) °C during the test. The pH values at the end of BOD measurement were 7.25, 7.32 and 7.30 for test bottle 2, 3 and 4, respectively. These values were within the acceptable range (6.0 ~ 8.5 for pH) specified by the OECD guideline.

Results with reference substance:
The percentage biodegradations of the reference compound (Sodium benzoate) were 74.2 % after 7 days and 74.3 % after 14 days and were within the acceptable range (greater than 40 % after 7 days and 65 % after 14 days) specified by the OECD guideline.

The percentage biodegradations of test substance by BOD meter after 14 and 28 days

Sample Name Bottle No.  BOD Concentration (mgO2/L)
% Degradation a Average of
% Degradation
14 days 28 days 14 days 28 days 14 days 28 days
Abiotic control  1 NA b NA
Treatment 1  2 200 219 62.8 69 58.9 68
Treatment 2 3 183 219 56.4 69.1
Treatment 3 4 186 211 57.4 66
Inoculum blank
6 36.6 39.4 NA NA

a: ((BOD con. of treatment bot. - BOD con. of bot. 6) / (ThOD c of test substance × nominal con. d)) × 100

b: Not applicable

c: ThOD: 2.6 mg O2/L

d: Nominal conc.: 100.1, 99.9 and 100.0 mg/L(bottle 2, 3 and 4)

The percentage biodegradation of test substance based on the residual amount after 28 days

Residual amount (mg/L) % Degradationb
Abiotic control(Bottle 1)

Treatmenta

62.6 1.86

97

a: Average concentration of test substance in bottle 2, 3, 4

b: (con. of bot. 1 by analysis - average con. of bot. 2. 3. 4 by analysis) / (con. of bot. 1 by analysis)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance could be concluded as readily degradable by microorganisms in the aquatic environment. The average percentage biodegradation of the test substance by BOD measurement after 28 days was 68.0 ± 1.44 %, which was higher than the pass level of biodegradability (60%) specified by the OECD guideline.
Executive summary:

Microbial degradation of Phytosphingosine was performed for 28 days according to the OECD 301C, Ready Biodegradability-MITI (I) (adopted 1992) and in compliance with GLP.

The inoculum used in this study was collected from 11 sites in Korea including 5 rivers (Gangjeong, Mulgeum, Gwangju, Gapcheon, Paldang), 4 domestic sewage treatment plants (Dalseo, Gumi, Busan, Tancheon) and 2 industrial wastewater treatment plants (Dalseo, Yeosu). Fresh samples collected from these sites were incubated for over one month and the activated sludge greater than 10^7 cells/mL was used in this test.

The test included 1 abiotic control, 3 test item groups, 1 activity control and 1 inoculum blank. Reference compound, Sodium benzoate, was used to check the microbial activity of treated inoculums. Test substance and reference compound were about 100 mg/L (w/v) after correcting for purity. Oxygen uptake was measured by the BOD meter.

The percentage biodegradations of the test substance, Phytosphingosine, observed by BOD measurement were calculated in the range of 66.0 ~ 69.1 % and the average percentage biodegradation was 68.0 % after 28 days. Results indicate that the test substance is ready biodegradable in aqueous condition (>60% according to the guideline). The percentage biodegradation based on the residual amount of test substance by HPLC analysis was calculated to be 97.0 %.

The study fulfilled the validity criteria of the guideline and was considered reliable and adequate for the environmental hazard assessment.

Description of key information

The test substance could be concluded as readily degradable by microorganisms in the aquatic environment. The average percentage biodegradation of the test substance by BOD measurement after 28 days was 68.0 ± 1.44 %, which was higher than the pass level of biodegradability (60%) specified by OECD 301C.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

A reliable key study was available on microbial degradation of Phytosphingosine. The study was performed for 28 days according to OECD 301C, Ready Biodegradability-MITI (I) (adopted 1992) and in compliance with GLP. The inoculum used in this study was collected from 11 sites in Korea including 5 rivers (Gangjeong, Mulgeum, Gwangju, Gapcheon, Paldang), 4 domestic sewage treatment plants (Dalseo, Gumi, Busan, Tancheon) and 2 industrial wastewater treatment plants (Dalseo, Yeosu).

The test included 1 abiotic control, 3 test item groups, 1 activity control and 1 inoculum blank. Reference compound, Sodium benzoate, was used to check the microbial activity of treated inoculums. Test substance and reference compound were about 100 mg/L (w/v) after correcting for purity. Oxygen uptake was measured by the BOD meter.

The percentage biodegradations of the test substance, Phytosphingosine, observed by BOD measurement were calculated in the range of 66.0 - 69.1 % and the average percentage biodegradation was 68.0 % after 28 days. Results indicate that the test substance is ready biodegradable in aqueous condition (>60% according to the guideline). The percentage biodegradation based on the residual amount of test substance by HPLC analysis was calculated to be 97.0 %.

The study fulfilled the validity criteria of the guideline and was considered reliable and adequate for the environmental hazard assessment.