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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:
29 November 2011 - 27 December 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: “Degradability Test of Chemicals by Microorganisms, etc.” prescribed in “Methods of Testing New Chemical Substances"
Version / remarks:
Ordinance No. 0331-7 of Pharmaceutical and Food Safety Bureau dated March 31, 2011, 2011-03-29 Manufacturing Industries Bureau No. 5, Ordinance No. 110331009 of Policy Planning Division, Environmental Health Department
Deviations:
not specified
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sludge = surface water containing the surface soil of rivers, lakes, ponds, and inner seas, return sludge of sewage-treatment plants (collected from 10 places in Japan, mixture of all sources)
- Storage conditions and period: not specifically reported
- Concentration of sludge: The concentration of suspended substances of the activated sludge was 3810 mg/L.
- Preparation of inoculum for exposure: addition of synthesized sewage (glucose, peptone, and potassium dihydrogenphosphate were dissolved in purified water, followed by pH adjustment to 7.0+/-1.0) 19 h before use of the activated sludge in the test

Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: basic culture medium (as prescribed in 21. of JIS K 0102-2010)
- Test temperature: 25 +/- 1°C
- pH: 7.0
- pH adjusted: yes, to pH 7
- Aeration of dilution water: not reported
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Closed System Oxygen Consumption Measuring Device
Water bath (including the measurement unit): AI-0001 (Asahi Techneion)
Data processing device: OM7000A (Okura-Denki)
Test Container: Glass culture bottle
- Number of culture flasks/control: 1 (inoculium blank (mineral medium), activity (aniline), abiotic (water))
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: rotation stirring
- Measuring equipment: automatic Oxygen Consumption Measuring Device
- Details of trap for CO2: Soda Lime, No. 1 (Wako Pure Chemical Industry, for carbon dioxide absorption)

SAMPLING
- Sampling frequency: continuously
- Sampling method: automatic
- Sample storage before analysis: not relevant

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1
- Abiotic sterile control: 1 (test item in water, no sludge)
- Toxicity control: no
- Other: 1 activity control

OBSERVATIONS AND MEASUREMENTS
- During the culture period, the status of the test solutions was monitored visually every day.
- During the culture period, changes of BOD of the test solutions were measured continuously by use of a closed system oxygen consumption measuring device.
- Temperature of the water bath of the closed system oxygen consumption measuring device was recorded every day.

STATISTICAL METHODS: only means were calculated; no further statistical analysis of the data
Reference substance:
aniline
Key result
Parameter:
% degradation (O2 consumption)
Value:
92
Sampling time:
28 d

Status of Test Liquids

 

Test liquid

Status (visually checked)

pH

At start of culture

(Water + Investigational Substance) System

The investigational substance was insoluble.

-

(Sludge + Investigational Substance) System

The investigational substance was insoluble.

-

At completion of culture

(Water + Investigational Substance) System

Insoluble matters were seen.

-

(Sludge + Investigational Substance) System

No insoluble matters except sludge were seen.

Proliferation of the sludge was seen.

-

 

Analysis Results of Test Liquids

 

 

(Water + Investigational Substance) System

(Sludge + Investigational Substance) System

Theoretical amount

[1]

[2]

[3]

[4]

BOD*1

mg

0

83.4

81.4

81.3

89.4

Detected DOC level*1, 2and detection rate

mgC

1.7

0.6

0.7

0.5

23.7

%

7

3

3

2

-

Residual amount of Investigational Substance and residual rate (HPLC)

mg

29.2

0

0

0

30.0

%

97

0

0

0

-

*1: With regard to the (Sludge + Investigational Substance) System, the values are displayed after being subtracted by the value of the Sludge Blank System.

*2: With regard to the (Water + Investigational Substance) System, the values are displayed after being subtracted by the value of the water blank.

 

 

Degradability

 

 

(Sludge + Investigational Substance) System

[2]

[3]

[4]

Mean

BOD degradability

%

93

91

91

92

Investigational Substance degradability (HPLC)

%

100

100

100

100

 

No DOC degradability was calculated because the amount of the test substance exceeding the test concentration (100 mg/L) is not soluble in water.

 

Discussion

 

Proliferation of the sludge was seen at the time of completion of the culture.

In addition, in the quantitative analysis of the test substance, no peak equivalent to changed matters was detected on the HPLC chromatogram.

A trace amount of DOC was detected in the DOC analysis, which is likely due to slight dissolution of the test substance in the (Water + Investigational Substance) System, and likely derived from microorganisms that proliferated due to biodegradation of the test substance in the (Sludge + Investigational Substance) System.

Validity criteria fulfilled:
yes
Remarks:
see "overall remarks"
Interpretation of results:
readily biodegradable
Conclusions:
The substance was readily biodegradable in the conditions of this test.
Executive summary:

The ready biodegradability of the substance was investigated in a study conducted in accordance with the Japanese “Degradability Test of Chemicals by Microorganisms, etc.” prescribed in “Methods of Testing New Chemical Substances", which is similar to OECD TG 301C, and GLP. The concentration tested was 100 mg/L test substance, with a suspended solids concentration of 30 mg/L. Aniline was tested in a positive control and found to almost give the expected biodegradation after 14 days (i.e. 64%, very close to the pass level of 65%). The test substance biodegrades for 92% in the standard 28d test. No toxicity control was included. Based on the results of this test the substance can be regarded as 'readily biodegradable'.

Description of key information

It is concluded that the substance is readily biodegradable under the conditions of a test similar to the OECD 301C Modified MITI test (I).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The ready biodegradability of the substance was investigated in a study conducted in accordance with the Japanese “Degradability Test of Chemicals by Microorganisms, etc.” prescribed in “Methods of Testing New Chemical Substances", which is similar to OECD TG 301C, and GLP. The concentration tested was 100 mg/L test substance, with a suspended solids concentration of 30 mg/L. Aniline was tested in a positive control and found to almost give the expected biodegradation after 14 days (i.e. 64%, very close to the pass level of 65%). The test substance biodegrades for 92% in the standard 28d test. No toxicity control was included. Based on the results of this test the substance can be regarded as 'readily biodegradable'.

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