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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.
Reference:
Composition 0
Guideline:
other: Guideline not specified but based on 'Test Methods for Novel Chemical Substances'
Principles of method if other than guideline:
Guideline not specified but based on "Test Methods for Novel Chemical Substances".
Biodegradation calculated based on oxygen consumption.
GLP compliance:
not specified
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum / activated sludge:
Seed sludge was obtained from the Chemical Biotesting Center of the Chemicals inspection and Testing Institute, Japan.

- Method of preparation:
It is a mixture of sludge collected at ten different locations nationwide and incubated with 0.1 % synthetic wastewater for a week at the Chemical Biotesting Center. The seed sludge was further cultured for 4 weeks before use in the biodegradation test.

The obtained seed sludge was cultured with 0.1 % synthetic wastewater before use. The composition of the synthetic wastewater was 1 g glucose, 1 g polypeptone and 1 g/L potassium dihydrogen phosphate. Sludge was cultured in the AS-Treater, a commercially available small tank for activated sludge.

-Properties of seed sludge:
When the seed sludge was cultured for 2 months after procurement, the sludge had a slight yellow color, and its supernatant was clear. The sludge was cultured for 4 weeks before the biodegradation test.

Numerous, cloud-like biological flocs were observed. A microscopic examination according to the classification developed by Isamu Morishita1) revealed that the sludge contained:
Protozoa:
- Free swimming ciliates: Chilodonella, Vronena, Colpidium
- Creeping ciliate: Aspidisca
- Unidentified: 5 other protozoa, including a free swimming ciliate, were found but unidentified
Metazoa
- Asellus hilgendorfii, Rotifer potatoria, etc. were found.
Duration of test (contact time):
14 d
Initial conc.:
100 other: ppm
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST SYSTEMS:
The biodegradation test was carried out using the closed oxygen consumption measuring apparatus specified in the notification “Test Methods for Novel Chemical Substances (hereinafter referred to as the notification).” The amount of consumed oxygen was measured by a coulometer, which uses constant current to supply electrolytic oxygen

CULTURE CONDITIONS:
Culture conditions for the biodegradation test
Microbial source: Seed sludge collected at 10 different locations nationwide
Sludge concentration: MLSS 30 ppm
Pre-culture: None
Basal medium: BOD diluent [JIS K0102, 16(1)]
Sample concentration: test material 100 ppm (w/v)
Total volume: 300 mL/Jar
Culture temperature: 25 ± 1 °C
Culture period: 14 days (Closed Agitation F)
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
64.2
Sampling time:
2 wk
Details on results:
The activity of seed sludge described in 3.1 was determined by aniline degradability after 2 weeks of culture with 0.1 % synthetic wastewater. The result was:
MLSS before culture 30 ppm
Biodegradability BOD/ThOD: 64.2 %
ThOD for aniline: 283.2 ppm/ 100 ppm base

The aniline degradability of the seed sludge satisfied the standard (40%) specified by the notification and thus considered favorable for the use.

BIODEGRADABILITY:
The test material's biodegradability was measured three times using the same sample. The average of three measurements was used for analysis. The sample is poorly soluble in water and adheres to the container wall. This lead to variability in the results obtained. Usually, the highest measurement value should be used for analysis instead of an average of three measurements. However, the average value was used in this study.
Results with reference substance:
TOC of the test material, aniline and basal aerobic activity after 14 days of culture was calculated from TC and IC values and these are shown in table 1. Under the conditions of this study, the biodegradability of the test material was determined to be 58.5 % (BOD14/ThOD). A compound with biodegradability of 40 % or more, when determined by a coulometer after 14 days of culture, is considered passably highly degradable, therefore the test material is considered to be readily biodegradable.

The test material was almost insoluble in water during this study. During the biodegradation test, the test material was often found left on the container wall. As a result, measured degradability was considered variable. Most of residual compounds in the test container were from the test material, which was thought stuck to the container wall without being mixed with the sludge. By the TOC analysis, however, organic compounds were scarcely present in the test solution, suggesting that once mixed with sludge, the test material was quickly degraded. Therefore in conclusion the test material is a highly biodegradable compound.

Table 1: TOC of Test material, aniline and basal aerobic activity

 

TC

IC

TOC (ppm)

Peak height

TC (ppm)

Peak height

IC (ppm)

Sample

Correction for sludge

Sample

Correction for sludge

Basal aerobic activity

2.0

 

 

2.5

 

 

 

Aniline

6.5

4.5

3.6

15.0

12.5

4.4

-

Solution for test material degradability

determination

8.5

6.5

5.2

6.5

4.0

1.4

3.8

Table 2: True BOD

Culture period days

Test material

Aniline

Basal aerobic activity

7

104.7

270.0

13.0

14

176.0

288.0

17.0

Conclusions:
Under the conditions of this study, the test material was considered to be readily biodegradable.
Executive summary:

The study was conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The ready biodegradability of the test material was investigated in a study which was conducted in accordance with the unspecified guidelines but based on ''Test Method for Novel Chemical Substances''.

The test material was almost insoluble in water during this study. During the biodegradation test, the test material was often found left on the container wall. As a result, measured degradability was considered variable. Most of residual compounds in the test container were from the test material, which was thought stuck to the container wall without being mixed with the sludge. By the TOC analysis, however, organic compounds were scarcely present in the test solution, suggesting that once mixed with sludge, the test material was quickly degraded. A compound with biodegradability of 40 % or more, when determined by a coulometer after 14 days of culture, is considered passably highly degradable, therefore the test material (58.5 %) is considered to be readily biodegradable.

Therefore in conclusion the test material is a highly biodegradable compound.

Description of key information

Under the conditions of this study, the test material was considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

The study was conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The ready biodegradability of the test material was investigated in a study which was conducted in accordance with the unspecified guidelines but based on ''Test Method for Novel Chemical Substances''.

The test material was almost insoluble in water during this study. During the biodegradation test, the test material was often found left on the container wall. As a result, measured degradability was considered variable. Most of residual compounds in the test container were from the test material, which was thought stuck to the container wall without being mixed with the sludge. By the TOC analysis, however, organic compounds were scarcely present in the test solution, suggesting that once mixed with sludge, the test material was quickly degraded. A compound with biodegradability of 40 % or more, when determined by a coulometer after 14 days of culture, is considered passably highly degradable, therefore the test material (58.5 %) is considered to be readily biodegradable.

Therefore in conclusion the test material is a highly biodegradable compound.