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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:
Study conducted between 23 December 2010 and 06 April 2011
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))
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Identity: ESA
Chemical name: 1,3,2-Dioxathiolane, 2,2-dioxide
Batch/Lot No.: Not applicable
Date received: November 30, 2010
Purity: 99.1%
Appearance: Pale yellow powder
Storage condition: Cold
Expiry date: October, 2013
Oxygen conditions:
aerobic
Inoculum or test system:
other: mixture of inoculum collected from rivers, domestic sewage treatment plants and industrial wastewater treatment plants
Details on inoculum:
Inoculum used in the biodegradation test was collected from 15 sites including rivers, domestic sewage treatment plants and industrial wastewater treatment plants in Korea. These samples were aerated and pooled for one month and then used in this test as the inoculum.
Duration of test (contact time):
28 d
Initial conc.:
30 other: ppm
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Preparation of basal culture medium
The composition of basal culture medium was as follows. Each solution A, B, C, and D was added to BOD bottles at a ratio of 450 μL per 150 mL.
Solution A:
Dipotassium hydrogen orthophosphate, K2HPO4 - 2.175 g
Potassium dihydrogen orthophosphate, KH2PO4 - 0.85 g
Disodium hydrogen orthophosphate dodecahydrate, Na2HPO4.12H2O - 4.46 g
Ammonium chloride, NH4Cl - 0.17 g
Dissolved in deionized water and made up to 100 mL.
The pH value of the solution was adjusted to 7.2.

Solution B:
Magnesium sulphate heptahydrate, MgSO4.7H2O - 2.25 g
Dissolved in deionized water and made up to 100 mL.

Solution C:
Calcium chloride dihydrate, CaCl2.2H2O - 3.64 g
Dissolved in deionized water and made up to 100 mL.

Solution D:
Iron (III) chloride hexahydrate, FeCl3.6H2O - 0.025 g
Dissolved in deionized water and made up to 100 mL.
The pH value of the solution was adjusted to 7.2.

Experimental method
Test conditions
1. Concentration of test chemical : 30 ppm (w/v)
2. Amount of activated sludge : 6 mL (Number of viable cells ; greater than 10^7 cells/mL)
3. Temperature : 25±1°C
4. Period : 28 days
5. Performed in the dark condition

Experimental conduct
1. Microbial degradation by BOD meter
The experiment was performed in a BOD incubator using BOD meter. The six BOD bottles (500 mL) were prepared as below and aniline was used as a reference item to check the activity of the sludge. BOD meter was measured and recorded once a day.

Bottle 1 (Abiotic control) : Deionized water 150 mL + Test item 4.5 mg (30 ppm level)
Bottle 2, 3, 4 (Treatments) : Basal culture medium 144 mL + Activated sludge 6 mL + Test item 4.5 mg (30 ppm level)
Bottle 5 (Activity control) : Basal culture medium 144 mL + Activated sludge 6 mL + Aniline 15 mg (100 ppm level)
Bottle 6 (Inoculum blank) : Basal culture medium 144 mL + Activated sludge 6 mL

2. Treatment of activated sludge
Six mL of inoculum with number of viable cells greater than 10^7 cells (mL) was treated.
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
36
Sampling time:
28 d
Details on results:
The BOD concentrations of aniline and ESA were measured by BOD meter.The percentage biodegradation of the test item was 36.0% after 28 days.
Since test item in both abiotic control (Bottle 1) and treatments (Bottle 2, 3, 4) was not detected, the percentage biodegradation determined by GC could not be calculated. The result of recovery in establishment of analytical method was 86.9 ± 2.3%
Test temperature was maintained at 25.0 ± 0.3°C for 28 days and the pH values of treatments (bottle 2, 3, 4) were 6.6~7.0, after the end of the test. These pH values were within the acceptable range (6.0~8.5) specified by the OECD guidelines.
These results were obtained by the retest because the pH values of treatments (bottle 2, 3, 4) ranged from 3.7 to 4.8, which was not suitable for the criterion (6.0~8.5) of the OECD Guideline, at a level of 100 ppm of a previous test (before the retest). Thus, this test was conducted using a lower concentration of test item (30 ppm) in accordance with test guidelines.
Results with reference substance:
The results indicated that the percentage biodegradation of aniline was 64.5% after 7 days and 67.8% after 14 days. The percentage biodegradation of aniline determined by HPLC was calculated as 100% after 28 days.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The percentage biodegradation of the reference item, aniline, was within the acceptable range (higher than 40% after 7 days and 65% after 14 days) specified by the National Institute of Environmental Research Guidelines and the OECD guidelines. BOD concentrations of the inoculum blank (bottle 6) for 28 days were 0~48 mg O2/L. These values were within the acceptable range (less than 60 mg O2/L) specified by OECD guideline. The percentage biodegradation of the ESA observed by BOD meter was 36.0% after 28 days.
Therefore, the ESA could not be concluded as readily degradable by microorganisms in the aquatic environment based on the OECD pass level of biodegradability (60%).
Executive summary:

Objective

The objective of this study is to understand the readily biodegradability of the ESA in the aquatic environment.

Test Guidelines

Section 3.1, biodegradation test method of the Testing Guidelines for Toxicology Studies and in compliance with TCCA-Good Laboratory Practice Standards and Test Guidelines” (Notification No. 2010-29, issued by the National Institute of Environmental Research, Korea on August 16, 2010).

OECD, 1992.7.17, OECD Guidelines for Testing of Chemicals, TG No. 301C, MODIFIED MITI TEST (I) “Ready Biodegradability”. .

Result

The percentage biodegradation of the ESA observed by BOD meter was 36.0% after 28 days.

Therefore, the ESA could not be concluded as readily degradable by microorganisms in the aquatic environment based on the OECD pass level of biodegradability (60%).

Description of key information

The substance was tested according to OECD 301C, and after 28 days 36% degradation was reported by BOD meter. The test item could not be detected by GC in the abiotic control or treatments and therefore biodegradation could not be determined by this method. As only 36% degradation was reported by BOD, the substance cannot be identified as readily biodegradable according to this test.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information